The document discusses forensic DNA typing. It begins by explaining that forensic DNA typing identifies individuals by their DNA profiles and is a powerful investigative tool used to solve crimes. It then provides details on the history and science of DNA, including its structure, how it is inherited, different DNA tests used, and challenges in DNA analysis. The document also outlines best practices for collecting, packaging, transporting, and documenting DNA evidence at crime scenes.
Interpretation of dna typing results and codis Neha Agarwal
An STR genotype is the allele, in the case of a homozygote, or alleles, in the
case of a heterozygote, present in a sample for a particular locus and is normally
reported as the number of repeats present in the allele. A full sample genotype
or STR profi le is produced by the combination of all of the locus genotypes into
a single series of numbers. This profi le is what is entered into a case report or
a DNA database for comparison purposes to other samples.
The document discusses the history and techniques of forensic DNA analysis. It describes how early methods like RFLP used repeated DNA regions called VNTRs to differentiate individuals. More recent STR techniques use short tandem repeats that allow analysis of low-quantity and degraded DNA samples. The document provides an overview of DNA structure and function, describing the double helix structure and how DNA is organized into chromosomes, genes, and loci. It also summarizes sample collection sources for DNA analysis and the basic workflow from extraction to profiling and comparison.
Human identification from DNA is typically based
on 13 short-tandem repeat (STR) alleles. Commercial kits used in forensic casework rely on the detection of these alleles in DNA samples acquired from an individual. However, the process itself is slow (it can take up to 2 days when conducting a laboratory analysis or 1 hour when using Rapid DNA systems) and has been designed to operate on pristine DNA samples. The need for
achieving fast and accurate DNA processing has spurred efforts in developing portable systems that can reduce the processing time to less than 1 hour. But such systems are expected to operate on degraded DNA samples due to the architecture and process used by the instrument. Consequently, detecting the alleles in such degraded DNA samples can be a challenging problem. In this paper, we present an algorithm to detected allelic peaks from degraded DNA signals based on an adaptive signal processing scheme.
Forensic Sciences (DNA Fingerprinting) STR Typing - Case Reportnarmeenarshad
Identification of Human Remains by DNA Analysis of the gastrointestinal contents of Fly Larvae
A case Report that has been explained in form of presentation.
Forensic significance of DNA Profiling (Forensic biology) Shabnamkhan113
This document discusses the forensic significance of DNA profiling and its applications in various cases. DNA profiling can help solve disputed paternity cases, identify child swapping incidents, assist in veterinary and wildlife cases, analyze plant evidence, and identify missing persons. Specific techniques discussed include VNTRs, STRs, Y-STRs, and mitochondrial DNA analysis which can be used to include or exclude suspects in criminal investigations. DNA evidence left at crime scenes can provide crucial links between victims, suspects, and locations to solve crimes.
DNA contains genetic information that can be used to identify individuals. DNA profiling isolates variable regions of DNA to create unique fingerprints. Samples are collected, amplified through PCR, separated via electrophoresis, and compared to reference profiles to identify matches or eliminate suspects. DNA analysis is a highly accurate forensic technique used to solve crimes and identify remains.
DNA contains genetic information that codes for proteins. It is found in the nucleus of cells in structures called chromosomes. DNA differs between individuals at certain locations called loci. Forensic DNA analysis involves extracting DNA from evidence samples, amplifying regions of interest using PCR, separating the amplified DNA, and comparing it to reference samples. If DNA matches between an evidence sample and suspect, statistics are presented on the estimated frequency of that DNA profile in a population. Mitochondrial DNA analysis can be used for degraded samples and examines DNA sequence rather than length.
Parental testing is considered one of the best ways to establish a biological parent child relation between individuals
Do you believe that your partner is currently
being unfaithful?
Interpretation of dna typing results and codis Neha Agarwal
An STR genotype is the allele, in the case of a homozygote, or alleles, in the
case of a heterozygote, present in a sample for a particular locus and is normally
reported as the number of repeats present in the allele. A full sample genotype
or STR profi le is produced by the combination of all of the locus genotypes into
a single series of numbers. This profi le is what is entered into a case report or
a DNA database for comparison purposes to other samples.
The document discusses the history and techniques of forensic DNA analysis. It describes how early methods like RFLP used repeated DNA regions called VNTRs to differentiate individuals. More recent STR techniques use short tandem repeats that allow analysis of low-quantity and degraded DNA samples. The document provides an overview of DNA structure and function, describing the double helix structure and how DNA is organized into chromosomes, genes, and loci. It also summarizes sample collection sources for DNA analysis and the basic workflow from extraction to profiling and comparison.
Human identification from DNA is typically based
on 13 short-tandem repeat (STR) alleles. Commercial kits used in forensic casework rely on the detection of these alleles in DNA samples acquired from an individual. However, the process itself is slow (it can take up to 2 days when conducting a laboratory analysis or 1 hour when using Rapid DNA systems) and has been designed to operate on pristine DNA samples. The need for
achieving fast and accurate DNA processing has spurred efforts in developing portable systems that can reduce the processing time to less than 1 hour. But such systems are expected to operate on degraded DNA samples due to the architecture and process used by the instrument. Consequently, detecting the alleles in such degraded DNA samples can be a challenging problem. In this paper, we present an algorithm to detected allelic peaks from degraded DNA signals based on an adaptive signal processing scheme.
Forensic Sciences (DNA Fingerprinting) STR Typing - Case Reportnarmeenarshad
Identification of Human Remains by DNA Analysis of the gastrointestinal contents of Fly Larvae
A case Report that has been explained in form of presentation.
Forensic significance of DNA Profiling (Forensic biology) Shabnamkhan113
This document discusses the forensic significance of DNA profiling and its applications in various cases. DNA profiling can help solve disputed paternity cases, identify child swapping incidents, assist in veterinary and wildlife cases, analyze plant evidence, and identify missing persons. Specific techniques discussed include VNTRs, STRs, Y-STRs, and mitochondrial DNA analysis which can be used to include or exclude suspects in criminal investigations. DNA evidence left at crime scenes can provide crucial links between victims, suspects, and locations to solve crimes.
DNA contains genetic information that can be used to identify individuals. DNA profiling isolates variable regions of DNA to create unique fingerprints. Samples are collected, amplified through PCR, separated via electrophoresis, and compared to reference profiles to identify matches or eliminate suspects. DNA analysis is a highly accurate forensic technique used to solve crimes and identify remains.
DNA contains genetic information that codes for proteins. It is found in the nucleus of cells in structures called chromosomes. DNA differs between individuals at certain locations called loci. Forensic DNA analysis involves extracting DNA from evidence samples, amplifying regions of interest using PCR, separating the amplified DNA, and comparing it to reference samples. If DNA matches between an evidence sample and suspect, statistics are presented on the estimated frequency of that DNA profile in a population. Mitochondrial DNA analysis can be used for degraded samples and examines DNA sequence rather than length.
Parental testing is considered one of the best ways to establish a biological parent child relation between individuals
Do you believe that your partner is currently
being unfaithful?
Anthropology is the systematic study of humankind. Forensic anthropology involves the examination of human remains to identify individuals and determine cause of death. It can provide biological profiles, help distinguish trauma timing, and match remains to missing persons cases. New applications include using 2D images to identify suspects, 3D facial modeling, and assessing images for age in legal cases.
This document provides an introduction to forensic biology. It discusses how forensic science applies various scientific disciplines to criminal and civil law. Forensic biology is a branch of forensic science that utilizes biology, and has several sub-disciplines including forensic serology, DNA fingerprinting, forensic anthropology, and forensic entomology. These specializations analyze evidence like blood, semen, hair, and insects to identify individuals and determine details about crime scenes. Forensic scientists play an important role in the criminal justice system by using scientific analysis to help investigate crimes.
DNA profiling, also known as DNA fingerprinting or DNA typing, is a forensic technique used to identify individuals by characteristics of their DNA. It involves extracting DNA from a sample, analyzing locations in the DNA that are variable between individuals to create a DNA profile, and comparing that profile to others to see if there is a match. Alec Jeffreys discovered in 1984 that restriction fragment length polymorphism (RFLP) analysis could be used to generate DNA profiles for personal identification. Additional techniques like polymerase chain reaction (PCR), short tandem repeats (STR), and mitochondrial DNA analysis were later developed to analyze smaller DNA samples. DNA profiling is now widely used in criminal investigations and identifying unknown remains.
This document provides an overview of DNA profiling and fingerprinting. It discusses how DNA was discovered to have a double helix structure, and how DNA fingerprinting works by analyzing variable regions of DNA to generate unique profiles. The document outlines the stages of DNA fingerprinting, from extracting DNA to generating bands patterns, and discusses applications like solving crimes, paternity testing, and identifying medical conditions. It provides an example of how DNA profiling can eliminate a suspect or link them to a crime scene.
This document discusses various body fluids and the presumptive and confirmatory tests used to identify them at a crime scene. It outlines tests for blood, saliva, urine, semen, fecal stains, and sweat. For blood, tests detect hemoglobin or heme compounds, including the luminol, fluorescein, phenolphthalein, Teichmann, and Takayama tests. Saliva tests identify the enzyme amylase, including using Phadebas tablets. Urine tests detect creatinine or urea. Semen tests identify acid phosphatase or prostate antigens. Fecal tests detect bilirubin breakdown products. And sweat can be identified using crystal violet dye interaction.
this is used in crime investigators for finding the evidences where there is lack of availability of evidence. some cells that was peeled off from our any parts of body will be seen in the crime scene and it is possible to find these kind of evidence form the crime scene.
This document provides an overview of different DNA typing methods used in forensic analysis, including their history, techniques, uses, and key developments. It discusses early methods like Restriction Fragment Length Polymorphism (RFLP) analysis and how newer Short Tandem Repeat (STR) analysis allows analysis from smaller DNA samples. STR analysis examines repeat regions that are highly variable between individuals. Additional methods covered include mitochondrial DNA analysis, Y-chromosome STR analysis, low copy number DNA analysis, and the use of CODIS for DNA databases. Key applications of DNA typing include criminal investigations, immigration eligibility, paternity testing, and medical and population genetics research.
FORENSIC DNA PROFILING: Strengths and LimitationsHezekiah Fatoki
1) The document summarizes a seminar presentation on forensic DNA profiling, its strengths and limitations. It discusses various DNA analysis techniques like STR, SNP, mtDNA and emerging areas like epigenetics.
2) It outlines the process of forensic DNA analysis from sample collection and DNA extraction to profiling and interpretation. Strengths include high discrimination and sensitivity but limitations include low DNA samples, mixtures and coincidental matches.
3) Future directions discussed include microfluidics, nanotechnology, DNA databases and phenotypic inference from DNA. While improvements are being made, current DNA analysis is valid when used carefully alongside other evidence.
This document provides an overview of the history and current methods of forensic DNA analysis. It discusses early methods like RFLP that required large DNA samples, the development of PCR that allowed analysis of smaller samples, and the current standard method using STR analysis of 13-15 loci that can determine a person's profile with a probability of 1 in 1 trillion. It covers DNA mixture interpretation challenges, the CODIS database system, and specialized techniques like mtDNA, Y-STR, and SNP analysis.
This document provides an introduction to hair as forensic evidence. It discusses the history of using hair in criminal investigations, the different types and structures of hair, growth phases, locations hair evidence can be found, and methods for collection, preservation, and forensic examination. Hair can be examined to determine characteristics like the species, sex, race, and in rare cases individualization of the person it came from. Various tests are used to analyze hair evidence microscopically and chemically.
DNA profiling, also known as DNA fingerprinting, is a technique used by forensic scientists to identify individuals using samples of their DNA. Alec Jeffreys invented the process in 1985 at the University of Leicester. DNA profiling involves breaking down cells to extract DNA, cutting the DNA into fragments using restriction enzymes, separating the fragments by size using gel electrophoresis, and analyzing the pattern of fragment distribution, which is unique to each individual except identical twins. DNA profiling can be used to solve crimes by comparing DNA samples from a crime scene to suspects, and to solve medical problems like determining parentage in paternity suits or inheritance cases.
This document discusses short tandem repeats (STRs) which are repeating sequences of 1-10 DNA bases that can be used as genetic markers. STRs are efficiently amplified by PCR and analyzed using fluorescent detection systems or silver-stained gels to identify alleles based on the number of repeats. STR testing results in peak patterns that are converted to genotypes for comparison between laboratories. STRs provide marker loci that can be used for linkage analysis to map genes, determine ancestry from Y-chromosome or surname tests, and for quality assurance such as confirming tissue samples.
A paternity test uses DNA profiling to determine if a man is the biological father of a child. DNA is collected from the mother, child, and possible father and compared using methods like PCR analysis or STR analysis. The test is over 99.9% accurate in identifying the biological father and 100% accurate when excluding a possible father. Results typically take 3-10 days but can take longer without the mother's sample.
Dna Fingerprinting And Forensic Applicationsdheva B
DNA fingerprinting is a technique used to identify individuals by their unique DNA patterns. It involves extracting DNA from samples, cutting the DNA into fragments using restriction enzymes, separating the fragments via electrophoresis, and comparing the band patterns to determine if two DNA samples match. DNA fingerprinting is used in paternity testing, criminal identification, and other forensic applications to compare DNA evidence from a crime scene to a suspect's DNA.
DNA is used in forensics to compare samples from crime scenes to suspects. Investigators collect DNA evidence using tools like swabs, scalpels, and tape lifts. Samples can come from blood, saliva, skin cells, and other sources. DNA is then analyzed using techniques like STR profiling, which examines 13 specific regions of nuclear DNA. Profiles are entered into CODIS, a national database, to search for matches to unknown suspects or link open cases. A match of 4-5 markers indicates a high probability of a match between the crime scene sample and suspect.
DNA profiling and its legal applications were discussed. Key points include:
1) DNA profiling involves analyzing variable repetitive sequences in non-coding regions to obtain a unique genetic profile for identification.
2) The first use of DNA fingerprinting in a criminal case in 1986 helped exonerate a falsely accused man.
3) DNA has significant forensic applications such as identifying suspects in murder, sexual assault, and disputed parentage cases.
4) DNA analysis also has legal implications including the right to privacy versus right to information in criminal investigations.
Portrait Parle via Bertillon System By G S ShaktawatG.S Shaktawat
The individualization of the human is very hard thing from the ages. People had done or invented certain ways for the proper individualization of the person. The Bertillon System is the first anthropological technique for individualization invented by Sir Bertillon.
This PPT contains the content mainly from the history to the decline of the Bertillon system. And the center point of the PPT is the Portrait Parle or Bertillonage.
This document provides an overview of forensic biology and biological evidence. It begins by explaining that biological evidence like blood, semen, and saliva can be found at crime scenes and help prove that a crime occurred. It then discusses the anatomy and physiology of various body systems that produce biological fluids like the circulatory, lymphatic, and reproductive systems. Specific biological fluids discussed in detail include blood, semen, and their components. The role of these fluids as evidence and various tests used to analyze them are also summarized.
This document summarizes the use of DNA in forensic medicine. It discusses how DNA analysis has helped solve crimes and identify victims. It reviews routine uses of DNA like criminal identification, paternity testing, and victim identification. It also discusses new applications like low copy number DNA, touch DNA, and rapid DNA devices. Finally, it discusses limitations, ethical issues, and the future potential of DNA in forensic analysis and databases.
1) DNA fingerprinting is a powerful forensic technique used to identify criminals through their unique DNA profiles. It was accidentally discovered in 1984 by Dr. Alec Jeffreys and has since helped solve thousands of criminal cases.
2) DNA fingerprinting analyzes variable regions in non-coding "junk DNA" that differ between individuals, known as variable number tandem repeats (VNTRs). DNA samples from a crime scene are compared to a suspect's DNA profile to identify matches or exclusions.
3) Some famous early cases solved using DNA fingerprinting include identifying Colin Pitchfork as the murderer in two 1980s rape and murder cases in the UK, and exonerating Richard Buckland who had falsely confessed to the crimes. The O
Anthropology is the systematic study of humankind. Forensic anthropology involves the examination of human remains to identify individuals and determine cause of death. It can provide biological profiles, help distinguish trauma timing, and match remains to missing persons cases. New applications include using 2D images to identify suspects, 3D facial modeling, and assessing images for age in legal cases.
This document provides an introduction to forensic biology. It discusses how forensic science applies various scientific disciplines to criminal and civil law. Forensic biology is a branch of forensic science that utilizes biology, and has several sub-disciplines including forensic serology, DNA fingerprinting, forensic anthropology, and forensic entomology. These specializations analyze evidence like blood, semen, hair, and insects to identify individuals and determine details about crime scenes. Forensic scientists play an important role in the criminal justice system by using scientific analysis to help investigate crimes.
DNA profiling, also known as DNA fingerprinting or DNA typing, is a forensic technique used to identify individuals by characteristics of their DNA. It involves extracting DNA from a sample, analyzing locations in the DNA that are variable between individuals to create a DNA profile, and comparing that profile to others to see if there is a match. Alec Jeffreys discovered in 1984 that restriction fragment length polymorphism (RFLP) analysis could be used to generate DNA profiles for personal identification. Additional techniques like polymerase chain reaction (PCR), short tandem repeats (STR), and mitochondrial DNA analysis were later developed to analyze smaller DNA samples. DNA profiling is now widely used in criminal investigations and identifying unknown remains.
This document provides an overview of DNA profiling and fingerprinting. It discusses how DNA was discovered to have a double helix structure, and how DNA fingerprinting works by analyzing variable regions of DNA to generate unique profiles. The document outlines the stages of DNA fingerprinting, from extracting DNA to generating bands patterns, and discusses applications like solving crimes, paternity testing, and identifying medical conditions. It provides an example of how DNA profiling can eliminate a suspect or link them to a crime scene.
This document discusses various body fluids and the presumptive and confirmatory tests used to identify them at a crime scene. It outlines tests for blood, saliva, urine, semen, fecal stains, and sweat. For blood, tests detect hemoglobin or heme compounds, including the luminol, fluorescein, phenolphthalein, Teichmann, and Takayama tests. Saliva tests identify the enzyme amylase, including using Phadebas tablets. Urine tests detect creatinine or urea. Semen tests identify acid phosphatase or prostate antigens. Fecal tests detect bilirubin breakdown products. And sweat can be identified using crystal violet dye interaction.
this is used in crime investigators for finding the evidences where there is lack of availability of evidence. some cells that was peeled off from our any parts of body will be seen in the crime scene and it is possible to find these kind of evidence form the crime scene.
This document provides an overview of different DNA typing methods used in forensic analysis, including their history, techniques, uses, and key developments. It discusses early methods like Restriction Fragment Length Polymorphism (RFLP) analysis and how newer Short Tandem Repeat (STR) analysis allows analysis from smaller DNA samples. STR analysis examines repeat regions that are highly variable between individuals. Additional methods covered include mitochondrial DNA analysis, Y-chromosome STR analysis, low copy number DNA analysis, and the use of CODIS for DNA databases. Key applications of DNA typing include criminal investigations, immigration eligibility, paternity testing, and medical and population genetics research.
FORENSIC DNA PROFILING: Strengths and LimitationsHezekiah Fatoki
1) The document summarizes a seminar presentation on forensic DNA profiling, its strengths and limitations. It discusses various DNA analysis techniques like STR, SNP, mtDNA and emerging areas like epigenetics.
2) It outlines the process of forensic DNA analysis from sample collection and DNA extraction to profiling and interpretation. Strengths include high discrimination and sensitivity but limitations include low DNA samples, mixtures and coincidental matches.
3) Future directions discussed include microfluidics, nanotechnology, DNA databases and phenotypic inference from DNA. While improvements are being made, current DNA analysis is valid when used carefully alongside other evidence.
This document provides an overview of the history and current methods of forensic DNA analysis. It discusses early methods like RFLP that required large DNA samples, the development of PCR that allowed analysis of smaller samples, and the current standard method using STR analysis of 13-15 loci that can determine a person's profile with a probability of 1 in 1 trillion. It covers DNA mixture interpretation challenges, the CODIS database system, and specialized techniques like mtDNA, Y-STR, and SNP analysis.
This document provides an introduction to hair as forensic evidence. It discusses the history of using hair in criminal investigations, the different types and structures of hair, growth phases, locations hair evidence can be found, and methods for collection, preservation, and forensic examination. Hair can be examined to determine characteristics like the species, sex, race, and in rare cases individualization of the person it came from. Various tests are used to analyze hair evidence microscopically and chemically.
DNA profiling, also known as DNA fingerprinting, is a technique used by forensic scientists to identify individuals using samples of their DNA. Alec Jeffreys invented the process in 1985 at the University of Leicester. DNA profiling involves breaking down cells to extract DNA, cutting the DNA into fragments using restriction enzymes, separating the fragments by size using gel electrophoresis, and analyzing the pattern of fragment distribution, which is unique to each individual except identical twins. DNA profiling can be used to solve crimes by comparing DNA samples from a crime scene to suspects, and to solve medical problems like determining parentage in paternity suits or inheritance cases.
This document discusses short tandem repeats (STRs) which are repeating sequences of 1-10 DNA bases that can be used as genetic markers. STRs are efficiently amplified by PCR and analyzed using fluorescent detection systems or silver-stained gels to identify alleles based on the number of repeats. STR testing results in peak patterns that are converted to genotypes for comparison between laboratories. STRs provide marker loci that can be used for linkage analysis to map genes, determine ancestry from Y-chromosome or surname tests, and for quality assurance such as confirming tissue samples.
A paternity test uses DNA profiling to determine if a man is the biological father of a child. DNA is collected from the mother, child, and possible father and compared using methods like PCR analysis or STR analysis. The test is over 99.9% accurate in identifying the biological father and 100% accurate when excluding a possible father. Results typically take 3-10 days but can take longer without the mother's sample.
Dna Fingerprinting And Forensic Applicationsdheva B
DNA fingerprinting is a technique used to identify individuals by their unique DNA patterns. It involves extracting DNA from samples, cutting the DNA into fragments using restriction enzymes, separating the fragments via electrophoresis, and comparing the band patterns to determine if two DNA samples match. DNA fingerprinting is used in paternity testing, criminal identification, and other forensic applications to compare DNA evidence from a crime scene to a suspect's DNA.
DNA is used in forensics to compare samples from crime scenes to suspects. Investigators collect DNA evidence using tools like swabs, scalpels, and tape lifts. Samples can come from blood, saliva, skin cells, and other sources. DNA is then analyzed using techniques like STR profiling, which examines 13 specific regions of nuclear DNA. Profiles are entered into CODIS, a national database, to search for matches to unknown suspects or link open cases. A match of 4-5 markers indicates a high probability of a match between the crime scene sample and suspect.
DNA profiling and its legal applications were discussed. Key points include:
1) DNA profiling involves analyzing variable repetitive sequences in non-coding regions to obtain a unique genetic profile for identification.
2) The first use of DNA fingerprinting in a criminal case in 1986 helped exonerate a falsely accused man.
3) DNA has significant forensic applications such as identifying suspects in murder, sexual assault, and disputed parentage cases.
4) DNA analysis also has legal implications including the right to privacy versus right to information in criminal investigations.
Portrait Parle via Bertillon System By G S ShaktawatG.S Shaktawat
The individualization of the human is very hard thing from the ages. People had done or invented certain ways for the proper individualization of the person. The Bertillon System is the first anthropological technique for individualization invented by Sir Bertillon.
This PPT contains the content mainly from the history to the decline of the Bertillon system. And the center point of the PPT is the Portrait Parle or Bertillonage.
This document provides an overview of forensic biology and biological evidence. It begins by explaining that biological evidence like blood, semen, and saliva can be found at crime scenes and help prove that a crime occurred. It then discusses the anatomy and physiology of various body systems that produce biological fluids like the circulatory, lymphatic, and reproductive systems. Specific biological fluids discussed in detail include blood, semen, and their components. The role of these fluids as evidence and various tests used to analyze them are also summarized.
This document summarizes the use of DNA in forensic medicine. It discusses how DNA analysis has helped solve crimes and identify victims. It reviews routine uses of DNA like criminal identification, paternity testing, and victim identification. It also discusses new applications like low copy number DNA, touch DNA, and rapid DNA devices. Finally, it discusses limitations, ethical issues, and the future potential of DNA in forensic analysis and databases.
1) DNA fingerprinting is a powerful forensic technique used to identify criminals through their unique DNA profiles. It was accidentally discovered in 1984 by Dr. Alec Jeffreys and has since helped solve thousands of criminal cases.
2) DNA fingerprinting analyzes variable regions in non-coding "junk DNA" that differ between individuals, known as variable number tandem repeats (VNTRs). DNA samples from a crime scene are compared to a suspect's DNA profile to identify matches or exclusions.
3) Some famous early cases solved using DNA fingerprinting include identifying Colin Pitchfork as the murderer in two 1980s rape and murder cases in the UK, and exonerating Richard Buckland who had falsely confessed to the crimes. The O
DNA is a powerful tool that can be used in legal matters to identify suspects, convict the guilty, and exonerate the innocent. DNA analysis examines variable regions of DNA, such as short tandem repeats (STRs), that differ between individuals. By analyzing 10-13 STR regions and comparing the DNA profiles produced, forensic scientists can determine whether crime scene DNA evidence matches a suspect's DNA with extremely high accuracy and reliability. This DNA fingerprinting technique is an effective way to identify perpetrators and exonerate the innocent in criminal investigations.
Importance Of Gene Cloning In Forensic ScienceZohaib HUSSAIN
Gene cloning is important for forensic science in several ways:
1. DNA profiling allows identification of individuals by their unique DNA sequences and can be used to identify suspects, exonerate the wrongly accused, identify victims, and establish relationships.
2. DNA identification is effective when multiple variable regions of DNA are analyzed and compared between evidence and suspect samples. A match across several regions makes it very unlikely another person would have the same profile.
3. Various DNA technologies are used in forensic investigations including RFLP, PCR, STR, and mitochondrial DNA analysis, each with their own advantages for analyzing different types and qualities of samples.
DNA can provide powerful evidence in criminal cases. It is found in cells and can be extracted from bodily fluids and tissues left at crime scenes. DNA profiling uses short tandem repeats found in DNA that are highly variable between individuals to create DNA fingerprints for identification. Law enforcement collects DNA samples from suspects, victims, and crime scenes which are then analyzed using PCR and capillary electrophoresis to develop DNA profiles. If profiles match, it can identify suspects or link them to crime scenes. The Sheena Bora case is an example where DNA evidence from skeletal remains was crucial to identifying the victim and solving the case.
- The document outlines a seminar presentation on using DNA analysis as evidence in criminal justice. It discusses the structure and replication of DNA molecules, how DNA stores genetic information, the steps of analyzing DNA evidence, and types of DNA evidence analysis like PCR, STR, Y-chromosome, and mitochondrial analysis. It also addresses how DNA evidence is used in the criminal justice system and some challenges like degraded DNA samples. The conclusion emphasizes how DNA technology has expanded criminal investigations but there are still limitations to overcome.
The document discusses DNA forensic studies and DNA databases. It summarizes that experts conclude DNA forensic expertise should be extended beyond specialists to all law enforcement and the public. DNA can help solve cases but more evidence is sometimes needed to secure a conviction. DNA databases can help solve crimes but also raise privacy concerns as innocent people's DNA could be tracked. The pros and cons of DNA databanks are debated as they could help solve crimes but may invade privacy.
DNA profiling, also known as DNA fingerprinting, is a technique used by forensic scientists to identify individuals by characteristics in their DNA. The process was invented in 1985 by Alec Jeffreys at the University of Leicester. It involves extracting DNA from samples, cutting the DNA into fragments of varying lengths using restriction enzymes, separating the fragments by size using gel electrophoresis, and comparing the resulting patterns to DNA profiles in a database or from other samples. DNA profiling can be used to solve crimes by matching DNA evidence from a crime scene to suspects, and to solve medical problems like paternity testing.
DNA fingerprinting was developed in 1984 by Alec J. Jeffrey at the University of Leicester. It involves analyzing variable numbers of tandem repeats (VNTRs) in DNA to generate unique genetic profiles for identification purposes. DNA fingerprinting is now used for paternity testing, criminal investigations by comparing crime scene DNA to suspects' DNA, and identifying people or inherited health conditions through their DNA profile. While very accurate, DNA evidence requires careful analysis of potential random matches or errors and does not necessarily prove guilt on its own.
DNA fingerprinting is a technique that analyzes variations in DNA sequences at specific locations in the genome to identify individuals. There are two main methods: RFLP (restriction fragment length polymorphism) and PCR (polymerase chain reaction). RFLP involves digesting DNA with restriction enzymes, separating fragments by size, and detecting with probes. PCR amplifies specific DNA regions defined by primer sequences. Short tandem repeats (STRs) are now commonly analyzed by PCR. DNA fingerprinting is used in criminal investigations to identify suspects or victims, and in resolving medical issues like paternity disputes. DNA databases help law enforcement match crime scene evidence to suspects.
DNA analysis is a technique used to identify individuals by examining unique DNA sequences in their genomes. DNA profiles are created by scanning 13 specific regions of DNA and comparing samples from crime scenes to those of suspects. If the profiles match, it suggests the suspect was likely involved in the crime. DNA evidence has helped convict many criminals but also exonerate innocent people wrongly accused. Its use has prompted new laws regarding DNA collection and databases to solve crimes.
DNA fingerprinting was developed in 1984 by Alec J. Jeffrey at the University of Leicester. It is a technique used to distinguish individuals using DNA samples. It has many applications including identifying criminals, determining paternity, and diagnosing genetic diseases. The process involves isolating DNA from samples, cutting the DNA into fragments of different sizes with restriction enzymes, separating the fragments by size, and comparing fragment patterns to determine matches. DNA fingerprinting revolutionized identification and has been used to solve many criminal cases and identify remains.
DNA profiling was developed in 1984 by Sir Alec Jeffreys and involves analyzing variable regions of DNA called STRs or microsatellites that differ between individuals. It is used in forensic investigations to identify suspects or link them to crime scenes by comparing a sample to a reference DNA profile. The process involves extracting DNA from samples, analyzing STR regions to develop a profile of allele lengths, and entering it into DNA databases for comparison to other profiles. Some of the largest DNA databases are maintained by governments like the UK's NDNAD and US's CODIS, which help solve crimes but also raise privacy concerns due to retention of profiles.
DNA is the molecule that carries genetic instructions in organisms. In 1953, Watson and Crick discovered the double helix structure of DNA, which consists of two strands coiled around each other. Each strand is made up of a chain of nucleotides containing one of four bases - adenine, thymine, guanine and cytosine. The bases on one strand bond with complementary bases on the other strand through hydrogen bonds, with adenine bonding with thymine and guanine bonding with cytosine. This discovery revealed how genetic information is stored and replicated in cells.
DNA profiling is a technique used to distinguish individuals using DNA samples. It was invented in 1985 by Alec Jeffreys. The process involves breaking down cells to extract DNA, cutting the DNA into fragments using restriction enzymes, separating the fragments by size using gel electrophoresis, and analyzing the pattern of fragments to obtain a DNA profile. DNA profiling is used in criminal investigations to identify suspects by comparing crime scene DNA to suspects' profiles. It is also used to determine biological relationships in cases of paternity, maternity, and inheritance disputes. Famous cases that utilized DNA profiling include identifying Colin Pitchfork as the first criminal caught this way and the O.J. Simpson murder trial.
DNA can be used for identification purposes because every individual has a unique DNA sequence. DNA evidence is now commonly used in legal cases to determine guilt or innocence. DNA profiling involves comparing the DNA profile from a sample to that of another sample of known characteristics. It is used widely in healthcare, such as for diagnosing hereditary diseases, and in the legal system for identifying criminal suspects.
DNA Fingerprinting Explained, Techniques Used, Usage, Limitations and Contradictions.
*I won an Award for the Best Power Point Project Presentation in class 12th for this project. :D
DNA contains genetic information found in chromosomes in our cells. It is made up of a backbone, sugars, phosphates, and nitrogen base pairs (adenine pairs with thymine, and guanine pairs with cytosine). DNA is unique between individuals and can be used in forensic science to identify suspects and victims. DNA evidence can link suspects to crime scenes, eliminate suspects, identify victims through relatives, and connect multiple crime scenes to the same perpetrator. Factors like environment, heat, and bacteria can degrade DNA evidence over time. CODIS is a DNA database that can help identify suspects when no prior suspect existed.
1. Forensic DNA Typing
RANA MUHAMMAD ASIF
Ph D Scholar
Forensic Science and Molecular Biology
Forensic Scientist (DNA & Serology),
PUNJAB FORENSIC SCIENCE AGENCY
HOME DEPARTMENT
GOVERNMENT OF THE PUNJAB, PAKISTAN
2. The application of natural sciences to matters of criminal and civil laws
that are enforced by police agencies in the criminal justice system.
Scientific knowledge and technology are used to serve as witnesses in both
criminal and civil (intelligence) matters
Forensic science now has a prominent role in almost all criminal
investigations
Forensic science has shaped the world of justice, fuelling crime
investigations and signifying the progress of modern technology.
It provides accurate, thorough info to decision makers in our criminal
justice system.
Speedy DNA analysis enable police and LEAs to identify and arrest a
suspect in a very short period of time.
December 25, 2012 2
Forensic Science
3. Forensics
Derived from Latin word “forēnsis”
meaning : -
1. Pertaining to the law or justice system
2. Forum,
3. Place of assembly for legal trials/
judicial proceedings
4. Public discussion/ debate/
argumentation
December 25, 2012 3
4. 1. During the time of the Romans,
a criminal charge meant
presenting the case before the
public.
2. Both the person accused of the
crime & the accuser would give
speeches based on their side of
the story.
3. The individual with the best
argumentation would determine
the outcome of the case.
Forensics during the time of the Romans
December 25, 2012 4
5. December 25, 2012
Locard’s Exchange Principle
Dr Edmond Locard (1877-1966)
“Father of the Crime Lab”
Lyon, France
“Every contact leaves a trace”
5
Foundations of Forensic Science
The basic concept in Forensic Science
With contact between two items, there will
always be an exchange.
This is the basis of evidence collection at a
crime scene.
6. Wherever he steps, whatever he touches, whatever he leaves, even unconsciously,
will serve as a silent witness against him. Not only his fingerprints or his
footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool
mark he leaves, the paint he scratches, the blood or semen he deposits or collects.
All of these and more, bear mute witness against him. This is evidence that does
not forget. It is not confused by the excitement of the moment. It is not absent
because human witnesses are. It is factual evidence. Physical evidence cannot be
wrong, it cannot perjure itself, it cannot be wholly absent. Only human failure to
find it, study and understand it, can diminish its value.
Professor Edmond Locard
Basis of Locard’s Exchange Principle
December 25, 2012 6
7. When a criminal comes in contact with an object or person, a cross-transfer of
evidence occurs.
1. The suspect’s DNA deposited on the victim’s body or clothing;
2. The suspect’s DNA deposited on an object;
3. The suspect’s DNA deposited at a location;
4. The victim’s DNA deposited on suspect’s body or clothing;
5. The victim’s DNA deposited on an object;
6. The victim’s DNA deposited at a location;
7. The witness’ DNA deposited on victim or suspect; or
8. The witness’ DNA deposited on object or at location.
Dr. Henry Lee
December 25, 2012 7
How Evidences get Transfer
10. What is DNA?
1. Deoxyribonucleic acid
2. Nucleic acid that contains
the genetic instructions used in the
development and functioning of all
known living organisms.
3. Blueprint of life
December 25, 2012 10
11. DNA is a long molecule which looks like a ladder that is curled around
continuously and features about 3.2 billion rungs that attached to the ladder
and forms a double stranded helix. It is made from repeating units
called nucleotides held together with HB and consist of three types of
chemical components:
Simple sugar – deoxyribose Form Rails
Phosphate group (Run in opposite directions)
Four nitrogenous bases -Adenine (A)
- Guanine (G) Form Rungs
- Cytosine (C)
- Thymine (T)
The order in which these nucleotides are arranged on a strand of DNA is
unique to every individual person, making DNA a very efficient tool for the
identification of a person.
Structure of DNA
December 25, 2012 11
14. December 25, 2012 14
• 100 trillion cells
• 23 pairs of chromosomes
• 99.9% identical between
humans
• 0.1 % or 3 million bases
accounts for variation
• Est. 20,000 – 25,000
genes
Human Basic Genetics
15. Calculation of the quantity of DNA in a cell
1. Molecular Weight of a DNA Basepair = 618g/mol
A =: 313 g/mol; T: 304 g/mol; A-T base pairs = 617 g/mol
G = 329 g/mol; C: 289 g/mol; G-C base pairs = 618 g/mol
2. Molecular weight of DNA = 1.85 x1012 g/mol
There are 3 billion base pairs in a haploid cell ~3 x 109 bp
(~3 x 109 bp) x (618 g/mol/bp) = 1.85 x 1012 g/mol
3. Quantity of DNA in a haploid cell = 3 picograms
1 mole = 6.02 x 1023 molecules
(1.85 x 1012 g/mol) x (1 mole/6.02 x 1023 molecules)
= 3.08 x 10-12 g = 3.08 picograms (pg)
A diploid human cell contains ~6 pg genomic DNA
4. One ng of DNA contains the DNA from 167 diploid cells
1 ng genomic DNA (1000 pg)/6pg/cell = ~333 copies of each locus (2 per
167 diploid genomes)
December 25, 2012 15
16. DNAAnalogy
Genome = Book
Chromosome =Chapter
Gene = Paragraph
Exon = Sentence
Intron =Blank space
Nucleotides = Letters
December 25, 2012 16
17. Astonishing Comparisons That Elucidate
the Giant Data Capacity in DNA
1. If the information in the human genome could be
written down using the alphabet, it would fill
1,000 books of 1,000 pages each, each page
containing 3,000 letters. The DNA strand is
therefore approximately equal to 462 volumes of
the Encyclopedia Britannica
2. Someone working at a typewriter at a rate of 300
letters per minute for 8 hours a day, 220 days a
year, would take 95 years to complete the task.
3. According to Professor Leonard Adleman of Los
Angeles South California University, just 1 gram
(0.0022 pounds) of DNA can contain the
equivalent amount of data to 1 trillion CDs.
December 25, 2012 17
18. The earth is 150 billion m or 93 million miles
from the sun.
Astonishing Comparisons That
Elucidate the Giant molecule of DNA
1. Each cell has about 1.8 m of
DNA.
2. The average human has 100
trillion cells.
3. The average human has enough
DNA to go from the earth to the
sun more than 600 times.
4. DNA has a diameter of only
0.000000002 m.
December 25, 2012 18
19. December 25, 2012 19
Forensic DNA Typing
Forensic DNA Typing is a technology that identifies particular individuals by their
respective DNA profiles.
It is a scientific venture and powerful investigation tool to strengthen our war against the
vicious cycle of crimes and menace of terrorism using national DNA databases i.e.,
CODIS (USA), NDNAD (UK), INTERPOL DNA Database.
DNA fingerprinting has proven to be the most scientifically valid procedure for human
identification in forensic science.
It is the most powerful crime-fighting tool we have at our disposal.
DNA fingerprinting has been convicting criminals, and freeing the innocent, since 1985.
Forensic DNA typing is:
1. Solving the crimes,
2. Protecting the innocents
3. Identifying missing persons
4. Relationship testing
a) Paternity, Maternity
b) Grand Parantage Test
c) Siblingship test, Twin Zygosity Test
d) Ancestry
e) Genetic Reconstruction
20. December 25, 2012 20
DNA is preferably used as concrete evidence due to following
basic scientific facts: -
1. DNA does not tell lies
2. DNA can remain stable and typable for years
3. It is present in every cell (except RBCs)
4. The "genome" of any given individual (except for identical
twins and cloned organisms) is unique
5. The analysis of cells left at a scene allows for the DNA
present to be profiled
6. DNA containing cells can be found in many different sources
of biological evidences
Why DNA as evidence?
21. December 25, 2012 21
1. DNA profiling is a highly valuable and relatively economical
forensic identification tool
2. Since 1986, it has successfully exonerated the innocents and
convicted the offenders.
3. Allow a large number of samples to compare with a high degree of
reliability.
4. Developing DNA profiling techniques fit more closely with
standard specifications
5. DNA profiling techniques are more applicable to the routine
analysis of crime scene samples, often obtained from high-volume
crime.
6. The growing DNA Databases allow to accurately and efficiently
match and manage the data.
Why forensic DNA profiling is important for LEAs?
22. December 25, 2012 22
Advantages of DNA Typing
UNSURPASSED DISCRIMINATORY POTENTIAL
1. Complete blood group testing allows discrimination of one person in
several thousand and HLA typing one in several million.
2. DNA typing can routinely provide exclusion probabilities on the
order of one in billions
EXQUISITE SENSITIVITY
1. DNA can be amplified from very low amount of DNA. Even
Compromised DNA sample can be very successfully typed.
2. Smaller sample sizes are adequate
3. Allows rather small samples to be split and submitted for testing to
more than one laboratory
23. December 25, 2012 23
Application to any body tissue
DNA testing can be conducted with any sample having
nucleated cells. For example hairs, semen, urine and saliva
DNA is stable in comparison to proteins
Resistant to degradation by common environmental insults
Advantages of DNA Typing
24. •Mixtures must be resolved if present
•DNA is often degraded
•Inhibitors to PCR and sample contamination
are often present
December 25, 2012 24
Challenges of DNA use in Forensic Cases
25. December 25, 2012 25
•Rapes,
•homicides,
•child molestation,
•Sodomy,
•Aggravated assaults,
•hit & run,
•burglaries,
•Robberies,
•Kidnappings
Cases in which DNA evidences can be used
•Matching suspect with evidence
•Paternity Testing
•Maternity Testing
•Post conviction DNA testing
•Missing persons Identification
•Mass disasters Investigation
•Historical investigations
•Military personnel's DNA Testing
26. •Blood Stains
•Semen Stains
•Chewing Gum
•Stamps & Envelopes
•Penile Swabs
•Sweaty Clothing
•Bone
•Teeth
•Hair
•Vaginal Secretions
Where DNA may be found?
• Hospital samples
• Clothing
• Bedding
• Weapons
• Cigarette butts
• Drinking cups
•Fingernail Scrapings
•Saliva
•Body tissues
•Condom etc
December 25, 2012 26
27. Collection & Preservation
1. Biological evidence should be
allowed to air dry before
packaging.
2. Biological evidence should be
packaged in paper bags.
3. Biological evidence should be
stored under laboratory
conditions as available resources
permit - or in a
cool, dry climate, free of moisture.
4. Place liquid items in collection
tubes and refrigerate
December 25, 2012 27
28. Preliminary Documentation and Evaluation of the Scene
When conducting a crime scene assessment:
•Talk to the first responding officer regarding hid/her observations and activities
•Determine the entry and exit points to the crime scene
•Document every person who is entering and exiting the crime scene and evaluate any
biohazardous safety issues that should be considered
•Identify possible locations and sources of DNA evidence
•Thoroughly document the scene with diagrams and photographs (with scale in view when
appropriate)
•Document if evidence is wet or dry when discovered
•Document any bloodstain patterns, with reference points, before collection
These factors can be very important to the future investigation of the case.
NOTE: An alternative light source may be used to locate stains, such as semen and saliva,
on evidence before the processing begins.
December 25, 2012 28
29. Personal Protection & Contamination
Biological material can contain pathogens such as:
•Hepatitis
•Syphilis
•Tuberculosis
•Gonorrhea
•Measles
•HIV
Assume that all stains, wet or dry, are infectious.
December 25, 2012 29
30. Personal Protection
To minimize contamination while collecting evidence at a crime scene,
use appropriate personal protective gear such as:
•Latex gloves
•Lab Coat
•Masks
•Goggles
December 25, 2012 30
31. Guidelines to Protect Yourself and the Evidence
To protect yourself from biohazards and to protect the evidence from becoming
contaminated:
• Use new gloves for each piece of evidence
•Use clean or new implements to manipulate the sample
•Minimize contact with the sample (use a swab or forceps, etc.).
•If possible allow evidence to dry before packaging
•Collect and package evidence separately
•Do not fold together a bloodstained garment
•AVOID DIRECT CONTACT with the evidence sample
•Avoid coughing, sneezing and talking over evidence
•Avoid touching your face, nose and mouth during processing of evidence
•Establish a secure location for the disposal of biohazardous material like used
gloves and disposable instruments
•Establish a secure temporary storage area for biological evidence on the
crime scene
December 25, 2012 31
32. General procedures for collecting DNA evidence
•Submit the entire item if possible
•Use a clean or disposable razor blade or scalpel to cut out or scrape the stain
•Air-dry the stain before packaging
•Use a new or clean razor blade or scalpel to cut out a control sample
•If cutting is not appropriate to collect the evidence, new swabs can be used.
•Collect and package evidence separately
•Appropriately label each package
•DO NOT fold a stained garment on itself (even if stains are dry). "Sandwich" the
garment between two pieces of clean paper, then fold the garment so that the
paper is protecting the stained garment
•Avoid direct contact with the evidence sample
December 25, 2012 32
33. Collection Methods for DNA Evidence
1. Collection of stained item itself
2. Scraping of dried stain
3. Tape lifting of dried stain
4. Swabbing of stain
December 25, 2012 33
34. Packaging and Transport of DNA Evidence
•Packaging in the breathing paper bags/ boxes, plastic bags only for
temporary storage and transport of very wet items
•Proper documentation and labeling of item (Location, association, Item
description, date, time, Collector’s identity, manner of collection and
storage info)
•Maintenance of chain of custody (chronological list of all the persons
who handled the evidence and mention of storage places) is even more
important for biological evidence
•Appropriate storage of evidence items
•Timely dispatch of evidence to crime lab
•Submission of investigation notes with DNA evidence
December 25, 2012 34
37. DQ-alpha
TEST STRIP
Allele = BLUE DOT
RFLP
AUTORAD
Allele = BAND
Automated STR
ELECTROPHEROGRAM
Allele = PEAK
Three generations of DNA testing
December 25, 2012 37
39. December 25, 2012 39
Short Tendam Repeats (STR)
1. Short tandem repeat (STR) also known as Simple sequence
repeat (SSR) are repetitive sequences of 2-7 base pairs
which continuously repeat end-to-end.
2. The number of times the STRs repeat varies noticeably in
each individual person and, therefore, allows for
identification.
3. In STR typing, size based DNA separation is performed to
resolve different alleles from one another.
4. The repetition of STR usually only needs to be counted up
to thirteen and it is at this point that we are able to make a
match in identity.
40. • Dinucleotide (CA) (CA) (CA)
• Trinucleotide (GCC) (GCC) (GCC)
• Tetranucleotide (AATG) (AATG) (AATG)
• Pentanucleotide (AGAAA) (AGAAA) (AGAAA)
• Hexanucleotide (AGTACA) (AGTACA) (AGTACA)
Tetranucleotides STRs are preferred in human identification
Types of STR Repeat Units
December 25, 2012 40
41. December 25, 2012 41
Examples of STRs
Target region
(short tandem repeat)
7 repeats
8 repeats
9 repeats
10 repeats
11 repeats
12 repeats
13 repeats
DNA Profile of this locus = 8,10
42. The repeat region is variable between samples while the flanking regions
where PCR primers bind are constant
AATG
7 repeats
8 repeats
AATG AATG
Homozygote = both alleles are the same length.
Heterozygote = alleles differ and can be resolved from one another.
Primer positions define PCR product size
Fluorescent
dye label
Short Tandem Repeats (STRs)
December 25, 2012 42
43. Why STRs are Preferred Genetic Markers
1. Rapid processing.
2. Abundant throughout the genome.
3. Highly variable within populations.
4. Small size range allows multiplex development.
5. Discrete alleles allow digital record of data.
6. Allelic ladders simplify interpretation.
7. PCR based which allows use of small amounts of DNA.
8. Small product size compatible with degraded DNA.
December 25, 2012 44
44. December 25, 2012 45
1. Sample Obtained from Crime Scene or Paternity Investigation
2. Screening for biological evidence
3. Extraction of DNA from biological samples
4. Quantification of the obtained DNA
5. Multiplex Amplification of the CODIS-required STR loci by the
polymerase chain reaction (PCR)
6. Separation and Detection of PCR products (STR Alleles)
7. Sample Genotype detection
8. Comparison of sample genotype to other sample results
9. If match occurs, comparison of DNA profile to population
databases
10. Generation of case report with probability of Random match
Steps in DNA Typing
45. Forensic serology deals with the scientific study of blood and other bodily fluids
that are found at crime scenes. This is primarily performed for the detection and
identification of biological material (i.e., blood, semen, saliva, and urine) on
physical evidence in order to:
1. Link suspect(s) and victim(s) to each other and/or to the scene(s)
2. Include or exclude potential suspect(s) or victim(s)
3. Establish crime scene(s)
4. Identify weapon(s)
5. Corroborate case circumstances
6. Narrow down the samples for further analysis
Forensic Serology
December 25, 2012 46
46. Serological Analyses
Analysts document the physical evidence, screen the
evidence thoroughly for the presence of biological
materials, and collect and preserve biological samples for
further analysis while upholding the integrity of the
evidence at all times. Based on the case information
provided and established casework management protocols,
scientists select an appropriate evidence processing scheme
which may involve chemical, enzymatic, immunological,
and/or microscopic techniques.
December 25, 2012 47
48. The first step in a serological examination is the documentation and visual
examination of evidence. Biological stains may, or may not, be visible to the
unaided eye. The alternate light source (ALS) allows the scientist to visualize
biological stains invisible to the naked eye. Performed in a darkened room
while wearing colored goggles, stains will fluoresce when viewed at different
wavelengths of visible light. Questioned stains are then subjected to the
appropriate presumptive and confirmatory tests, as described below.
Visual examination of evidence
December 25, 2012 49
49. A complex mixture of cells, enzymes, proteins &
inorganic substances
Fluid portion of blood is called the plasma (55% of blood
content)
primarily water
red cells (erythrocytes)
white cells (leukocytes)
platelets
Human Blood
December 25, 2012 50
50. Is it blood?
What species is it
from?
Individualization?
In criminal cases blood is the 1st most common fluid that is
found at the scenes of crime.
Blood Analysis
December 25, 2012 51
51. Screening Test:
1. Prostatic acid phosphatase
Confirmatory Test:
1) Microscopy (Staining)
2) ABAcard® P-30 Test Strips
In criminal cases semen is the 2nd most common fluid that is found at
the scene. Semen identification is very important part of: -
1. Rape,
2. Sodomy,
3. Bestiality,
4. False accusation by a women,
5. Incest and
6. Sexual murder cases.
Semen Analysis
December 25, 2012 52
52. Presumptive test for semen
The Acid Phosphatase (AP) Test is a presumptive test for
semen. Acid phosphatase is an enzyme that is present in
high concentrations in seminal material. If a purple color
change occurs within a minute, the test is considered
positive for the possible presence of semen. This is not a
conclusive test as AP is also found in other substances
(e.g., vaginal secretions, douches, and contraceptive
creams), although at lower concentrations.
Confirmatory tests for semen
1. Using compound microscopes, scientists search for
spermatozoa, or sperm cells, on slides prepared from
swabs, clothing, etc. The slides are stained using the
Kernechtrot-Picroindigocarmine Stain, or “Christmas
Tree Stain”, in which the heads of the spermatozoa are
colored red and the tails are colored green.
2. If spermatozoa are not detected, an extract of the stain
is tested for p30, a protein synthesized in the prostate
gland using two immunoassay methods: cross-over
electrophoresis and a rapid, membrane-based card test.
Semen Analysis
December 25, 2012 53
53. Semen
1. Mixture of sperm and the secretions of the seminal vesicles, prostate gland,
and the bulbourethral glands.
2. Sperm 10%, Seminal fluid 90% and Epithelial Cell < 1%.
3. Contains small amounts of more than thirty elements, including fructose,
ascorbic acid, cholesterol, creatine, citric acid, lactic acid, nitrogen, vitamin
B12, potassium Choline Phosphate, Proteases, free Amino Acids,
Ergothioniene, Zinc, Calcium, Spermine, Lipids, Enzymes like
Fibrinogenase, Diastase, Acid & Alkaline Phosphatase, Glysidases, a & ß
Mannosidases a & ß Glucosidases, ß Givcouridases and various salts.
4. pH of 7.2 to 8.0, sperm concentration of 20×106 spermatozoa/ml or more,
sperm count of 40×106 spermatozoa per ejaculate
5. The average speed of semen at the moment of ejaculation is 31 mph (Faster
than a West African Jaguar.)
6. Semen acts as an antidepressant for women.December 25, 2012 54
54. 1. About 0.05 mm long
2. Develop only within the testicles from a spermatogonium
3. Spermatogonium spermatocytes spermatids
mature spermatozoan
4. Develop with in 70 -74 days
5. A man usually produces between 10 and 50 million sperms/day
6. Around 200 million to 500 million spermatozoa are released per ejaculation
and make up only about 2–5% of the volume of semen.
7. sperm determines the sex of the offspring, chromosomal pair "XX” results in a
female while "XY" results a male child.
8. Sperm carry 18,000 male genes to the female’s egg.
9. Antoni van Leeuwenhoek first observed sperm cells in 1679.
10. Sperm swim at a rate of about 1 to 4 mm (0.12 inches) per minute and wave
their tales more than 1000 times just to swim 1.25 cm or a half an inch
11. Over the course of a man’s life, man produce more than 12 trillion sperm.
12. The no of days the sperm can live inside a woman = 5
Sperm
December 25, 2012 55
56. Steps Involved in DNA Casework Processing
Organic and Differential DNA
extraction
Separation of time and space for
evidence and reference samples
Real-Time PCR
Multiplex PCR with fluorescent labels
Capillary Electrophoresis
Crime scene DNA profile comparison
with victims, suspects or Database
December 25, 2012 57
59. The Problem:
How do we identify and detect a specific sequence in
a genome?
• TWO BIG ISSUES:
– There are a LOT of other sequences in a genome that
we’re not interested in detecting. (SPECIFICITY)
– The amount of DNA in samples we’re interested in is
VERY small. (AMPLIFICATION)
December 25, 2012 60
60. The Problem: Specificity
How do we identify and detect a specific sequence in a
genome?
• Pine: 68 billion bp
• Corn: 5.0 billion bp
• Soybean: 1.1 billion bp
• Human: 3.4 billion bp
• Housefly: 900 million bp
• Rice: 400 million bp
• E. coli: 4.6 million bp
• HIV: 9.7 thousand bp
December 25, 2012 61
61. Molecular Xeroxing of
targeted areas of DNA
determined to contain
information
Used in:
research
diagnostics
forensics
Polymerase Chain Reaction
December 25, 2012 62
62. What Is PCR?
In vitro technique
Amplification of specific DNA
sequence between two regions of
known sequence
Invented 1985 by Kary Mullis- Nobel
Prize in chemistry in 1993.
PCR is used to target and replicate any
segment of DNA.
Copy high numbers (1 trillion) of
target in 2-3 hours.
A technique that involves repeated
cycles of 3 steps:
Denature
Anneal
Extension
December 25, 2012 63
63. Overall Principle of PCR
DNA – 1 copy
Known sequenceSequence of interestKnown sequence
PCR
Lots of copies
December 25, 2012 64
64. Why PCR?
To ‘pull the needle out of the haystack’
Rapid & easy
Sensitive
Robust
Widespread applications
December 25, 2012 65
65. The Cycling Reactions
Denature: ‘separate D.S DNA’
Anneal: ‘stick primers to S.S DNA’
Extend: ‘make new DNA from template’
94 oC
60 oC
72 oC
Time
Temperature
Single Cycle
Typically 25-40 cycles
performed during PCR
94 oC 94 oC 94 oC
60 oC60 oC
72 oC72 oC
December 25, 2012 66
66. Components of Reaction
Template DNA
Taq
dTTP
dCTP dGTP
dATP
Primers
DNA Polymerase
dNTPs
MgCl2- required to activate
Taq Polymerase.
Buffer- salt and pH balanced.
Water
December 25, 2012 67
68. Annealing
Temperature: ~50-70C (dependant on the melting
temperature of the expected duplex)
Primers bind to their complementary sequences
5’3’
5’ 3’
Forward primer Reverse primer
December 25, 2012 69
69. Extension
Temperature: ~72C
Time: 0.5-3min
DNA polymerase binds to the annealed primers and
extends DNA at the 3’ end of the chain
5’ 3’
Taq
5’
5’
3’
Taq5’
December 25, 2012 70
79. DNA Separation Mechanism
+-
DNA-
DNA-
DNA-DNA-
DNA-
• Size based separation due to interaction of DNA molecules with entangled
polymer strands
• “Gel” is not attached to the capillary wall
• Pumpable -- can be replaced after each run
• Polymer length and concentration determine the separation characteristics
December 25, 2012 80
82. Internal Size Standard
500400300100 200 600
December 25, 2012 83
A sizing standard is used in all samples and allelic ladders. The known
standard is used to determine the size of the allelic ladders and the unknown
samples
Internal size standards serve two purposes:
1. Sizes of all fragments are established for a sample (relative fragment
units). This is accomplished by using the ISS to establish a correlation
coefficient, which is used to determine the size of sample fragments.
2. The ISS serves as an effective control and provides information about
instrument run conditions. For instance, if all of the peaks for the sizing
standard are not present, it suggests a temperature, run time, or injection
problem.
83. December 25, 2012 84
Allele Calls
Comparison of the unknown fragments to the migration pattern of the allelic
ladder allows determination of the genotype. Software programs use macros to
automatically make the comparison.
85. DNA Testing Requires References
DNA results from one sample are always measured relative to other samples
(called references) examined at the same sites along the DNA molecule.
1. Forensic casework: Evidence compared to suspect(s)
2. Paternity testing: Child compared to alleged father(s)
3. Airplane crash: Victim remains compared to living relative(s)
4. Genetic genealogy: Y-chromosome results compared between two or
more relatives
Without reference samples and a full understanding of the genetic past, no valid
comparisons can be made
No reference samples means no association or match and no reliable
conclusion!
December 25, 2012 86
87. Three Possible Outcomes
Match – Peaks between the compared STR profiles have the same
genotypes and no unexplainable differences exist between the samples.
Statistical evaluation of the significance of the match is usually
reported with the match report
Exclusion (Non-match) – The genotype comparison shows profile
differences that can only be explained by the two samples originating
from different sources.
Inconclusive – The data does not support a conclusion as to whether
the profiles match. This finding might be reported if two analysts
remain in disagreement after review and discussion of the data and it is
felt that insufficient information exists to support any conclusion.
December 25, 2012 88
88. How Statistical Calculations are Made
Generate data with set(s) of samples from desired
population group(s)
– Generally only 100-150 samples are needed to obtain reliable allele
frequency estimates
Determine allele frequencies at each locus
Count number of each allele seen
Allele frequency information is used to estimate the rarity
of a particular DNA profile
Homozygotes (p2), Heterozygotes (2pq)
Product rule used (multiply locus frequency estimates)
For more information, see Chapters 20 and 21 in Forensic DNA Typing, 2nd Edition
December 25, 2012 89
91. December 25, 2012
Source: National Institute of Justice
92
Time required for DNA testing
1. Turnaround time in US: 30 days at best, > 1year in
many states.
2. Turnaround time in UK: 23-30 days (goal: 7-14
days).