Northern blotting is a technique developed in 1977 to detect specific RNA sequences through electrophoresis, transfer to a membrane, and hybridization with a probe. RNA is extracted from tissue samples, separated by size via electrophoresis in an agarose gel, and transferred by capillary action to a nylon or nitrocellulose membrane where it binds. Probes are then hybridized to the RNA and detected through radiolabeling or fluorescence to study gene expression under different conditions.
DNA profiling is a technique used by scientists to distinguish individuals using DNA samples. It involves breaking down cells to extract DNA, amplifying small DNA samples, cutting the DNA into fragments using restriction enzymes, separating the fragments by size using gel electrophoresis to produce a fluorescent image of bands, and analyzing the pattern of fragment distribution.
DNA Microarray and Analysis of Metabolic Controlshilpa sharma
This document describes a study that used DNA microarrays to analyze changes in gene expression related to tryptophan metabolism in E. coli under different physiological conditions and genetic mutations. The study identified genes whose expression levels changed with tryptophan availability, tryptophan starvation, and inactivation of the tryptophan repressor. Only a small core set of operons including trp, mtr and aroH showed highly responsive changes in expression levels. mRNA levels for aromatic amino acid biosynthesis genes decreased with excess tryptophan, while only the tnaA-tnaB operon increased. The results provide quantitative validation of genes known to be involved in tryptophan metabolism.
DNA fingerprinting is a technique that allows identification of an individual from biological samples based on their unique DNA fingerprint. It works by detecting variations in short tandem repeats (STRs) in the DNA, which differ in length between individuals. The process involves extracting DNA from a sample, using restriction enzymes to cut the DNA at specific sites, separating the fragments via gel electrophoresis, and amplifying the STR regions via polymerase chain reaction to facilitate comparison to known DNA profiles. DNA fingerprinting has applications in forensics, paternity testing, and medical diagnosis of inherited disorders, but risks discrimination and privacy issues if not properly regulated and restricted.
This document provides an overview of nanopore sequencing. It begins by outlining the benefits of nanopore sequencing such as flexibility, single molecule sequencing, and cost-effectiveness. It then discusses the history and concept of nanopore sequencing, which was envisioned in the 1990s and involves using nanopores to sequence DNA strands. The document describes how Oxford Nanopore's technology uses protein nanopores embedded in membranes to detect the electrical signals of DNA as it passes through. It also explains the components involved, such as the biological or solid-state nanopore, array of microscaffolds, and sensor chip.
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
Northern blotting is a technique developed in 1977 to detect specific RNA sequences through electrophoresis, transfer to a membrane, and hybridization with a probe. RNA is extracted from tissue samples, separated by size via electrophoresis in an agarose gel, and transferred by capillary action to a nylon or nitrocellulose membrane where it binds. Probes are then hybridized to the RNA and detected through radiolabeling or fluorescence to study gene expression under different conditions.
DNA profiling is a technique used by scientists to distinguish individuals using DNA samples. It involves breaking down cells to extract DNA, amplifying small DNA samples, cutting the DNA into fragments using restriction enzymes, separating the fragments by size using gel electrophoresis to produce a fluorescent image of bands, and analyzing the pattern of fragment distribution.
DNA Microarray and Analysis of Metabolic Controlshilpa sharma
This document describes a study that used DNA microarrays to analyze changes in gene expression related to tryptophan metabolism in E. coli under different physiological conditions and genetic mutations. The study identified genes whose expression levels changed with tryptophan availability, tryptophan starvation, and inactivation of the tryptophan repressor. Only a small core set of operons including trp, mtr and aroH showed highly responsive changes in expression levels. mRNA levels for aromatic amino acid biosynthesis genes decreased with excess tryptophan, while only the tnaA-tnaB operon increased. The results provide quantitative validation of genes known to be involved in tryptophan metabolism.
DNA fingerprinting is a technique that allows identification of an individual from biological samples based on their unique DNA fingerprint. It works by detecting variations in short tandem repeats (STRs) in the DNA, which differ in length between individuals. The process involves extracting DNA from a sample, using restriction enzymes to cut the DNA at specific sites, separating the fragments via gel electrophoresis, and amplifying the STR regions via polymerase chain reaction to facilitate comparison to known DNA profiles. DNA fingerprinting has applications in forensics, paternity testing, and medical diagnosis of inherited disorders, but risks discrimination and privacy issues if not properly regulated and restricted.
This document provides an overview of nanopore sequencing. It begins by outlining the benefits of nanopore sequencing such as flexibility, single molecule sequencing, and cost-effectiveness. It then discusses the history and concept of nanopore sequencing, which was envisioned in the 1990s and involves using nanopores to sequence DNA strands. The document describes how Oxford Nanopore's technology uses protein nanopores embedded in membranes to detect the electrical signals of DNA as it passes through. It also explains the components involved, such as the biological or solid-state nanopore, array of microscaffolds, and sensor chip.
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
This document discusses variable number tandem repeats (VNTRs), specifically microsatellites and minisatellites. It defines VNTRs as sequences with a variable number of tandem repeats of short DNA motifs. Microsatellites have repeat units of 1-10 bp while minisatellites have larger repeat units of 9-65 bp. Minisatellites can be detected using Southern blots with probes targeting the core repeat sequence, while microsatellites are detected using PCR. VNTRs are highly polymorphic due to variations in the number of repeats, making them useful for applications like forensic analysis, genetic mapping, and varietal identification.
The chain-termination method developed by Frederick Sanger and coworkers in 1977. This method used fewer toxic chemicals and lower amounts of radioactivity than the Maxam and Gilbert method. Because of its comparative ease, the Sanger method was soon automated and was the method used in the first generation of DNA sequencers.
Types of Restriction Endonuclease enzymesNishanth S
Restriction enzymes are produced by bacterial cells to protect themselves from foreign DNA. There are three main activities of restriction enzymes: recognition, digestion, and modification. Restriction enzymes are classified into three groups based on their source and biochemical activity: isoschizomers which have the same recognition and cleavage sites, neoschizomers which have the same recognition site but different cleavage sites, and isocaudomers which have different recognition sites but the same cleavage sites.
Dna replication and enzymes involved in dna replicationNarayan Prahlad
DNA replication is the process by which DNA copies itself. It requires DNA polymerase enzymes, primers, and deoxynucleotide triphosphates. DNA polymerase adds nucleotides to the 3' end of the primer according to the DNA template. Replication occurs through the coordinated action of helicase, DNA polymerase, primase, ligase, and other proteins. DNA polymerase proofreads newly synthesized DNA to ensure high fidelity. The coordinated actions of these enzymes and proteins precisely duplicate the genome during semi-conservative replication.
This document summarizes three main next generation sequencing technologies: Roche/454FLX pyrosequencing, Illumina/Solexa sequencing by synthesis, and Applied Biosystems SOLiD sequencing by ligation. Pyrosequencing works by detecting pyrophosphate released during DNA polymerization, producing light signals to determine the sequence. Roche/454FLX amplifies DNA fragments on beads in emulsions and sequences in picotiter plates. Illumina attaches DNA fragments to a flow cell for bridge amplification and sequencing by synthesis. Applied Biosystems SOLiD performs sequencing by ligation, determining sequences through sequential ligation of oligos.
The document summarizes the application of recombinant DNA technology in forensic science. It discusses how DNA analysis using techniques like PCR, STR, RFLP, and mtDNA can be used to analyze biological evidence from crime scenes to identify individuals. DNA profiling has become an important tool in forensic investigations to solve crimes and legal cases involving issues like identification, paternity testing, and exoneration of suspects. The document also provides examples of different biological materials that can be tested and discusses how DNA databases like CODIS are used to match crime scene evidence to known offender profiles.
This document is a biochemistry assignment submitted by Nibedita Ayan, an MBBS student at Xiamen Medical College, China under the guidance of Dr. A. K. M. Arif Uddin Ahmed. The assignment discusses nucleic acids, their discovery, structure, roles, and impacts. It covers topics such as nucleic acids carrying hereditary information and acting as carriers of genes, DNA and RNA having different but important roles, the central dogma of biology regarding DNA transcription and protein synthesis, DNA replication enabling species continuation, and various aberrations in nucleic acids like mutations, which can impact evolution, cancer development, and more.
DNA sequencing determines the precise order of nucleotides in a DNA fragment. There are several methods for DNA sequencing, including the chain termination method developed by Sanger, and the Maxam-Gilbert chemical cleavage method. Next generation sequencing is now used, which allows high-throughput sequencing of entire genomes quickly and accurately using automated methods. DNA sequencing has many applications, such as identifying disease-causing genes and mutations.
DNA, or deoxyribonucleic acid, is the hereditary material found in humans and most organisms that contains the genetic instructions used in the development and functioning of living beings. DNA is located in the cell nucleus for eukaryotic cells like humans, but in the cytoplasm for prokaryotic cells like bacteria. DNA is composed of nucleotides containing phosphate, sugar, and nitrogen bases that form the signature double helix structure. The sequence of these bases determines the organism's traits and functions. DNA analysis has various important applications in fields like genetics, medicine, agriculture, law, and archaeology.
DNA is highly compacted in cells through various levels of supercoiling and chromatin structure. At the most basic level, DNA wraps around histone proteins to form nucleosomes, introducing negative supercoiling. Nucleosomes are then packed into a beads-on-a-string structure and further compacted into the 30nm fiber. Additional folding compacts the DNA over 10,000-fold into the final chromosomes. The two main types of supercoiling that facilitate compaction are plectonemic and solenoidal, with solenoidal supercoiling allowing the greatest degree of compaction and found in chromatin.
DNA fingerprinting is a technique used for identification by extracting and analyzing the base pair pattern of an individual's DNA. It involves isolating DNA from a sample, cutting the DNA into fragments using restriction enzymes, and comparing the fragment patterns on a gel to identify individuals. The main applications of DNA fingerprinting are in solving criminal cases by matching DNA evidence to suspects, diagnosing inherited diseases, and determining biological relationships in areas like paternity testing.
1) DNA fingerprinting is a technique used to identify individuals by their unique DNA patterns. It analyzes Variable Number Tandem Repeats (VNTRs) in DNA, which vary between people.
2) The Southern blot technique is used to detect and analyze VNTRs. It involves extracting DNA from a sample, cutting it, separating fragments by size, and probing for specific VNTRs.
3) PCR (polymerase chain reaction) is used to amplify small DNA samples. It heats and cools DNA in cycles to make billions of copies of specific DNA regions for analysis.
This document summarizes various mechanisms of DNA repair. It discusses sources of DNA damage including exogenous sources like radiation and chemicals, and endogenous sources like oxidation. It describes different types of DNA damage such as oxidation, deamination, alkylation, and dimerization. The key DNA repair mechanisms discussed are direct reversal, base excision repair, nucleotide excision repair, mismatch repair, and double-strand break repair. The document emphasizes that without proper DNA repair, damage can lead to genomic instability and disease.
DNA and RNA are nucleic acids that are essential for life. DNA contains the genetic instructions used in the development and functioning of all living organisms. It is a double-stranded molecule found in the nucleus of cells. RNA is a single-stranded molecule that helps carry out the instructions specified by DNA, such as synthesizing proteins. The four bases found in DNA are adenine, guanine, cytosine, and thymine, while RNA contains adenine, guanine, cytosine, and uracil. Watson and Crick discovered that DNA has a double helix structure in 1951. Their model showed how the bases on each strand are paired through hydrogen bonding in a complementary way.
RNASeq - Analysis Pipeline for Differential ExpressionJatinder Singh
RNA-Seq is a technique that uses next generation sequencing to sequence RNA transcripts and quantify gene expression levels. It can be used to estimate transcript abundance, detect alternative splicing, and compare gene expression profiles between healthy and diseased tissue. Computational challenges include read mapping due to exon-exon junctions and normalization of read counts. Key steps in RNA-Seq analysis include read mapping, transcript assembly, counting and normalizing reads, and detecting differentially expressed genes.
Basics of molecular biology tools and techniquesBOTANYWith
The key players in molecular biology are DNA, RNA, and proteins. DNA is the blueprint stored in the genome that contains the genetic instructions. It is replicated for cell division. During transcription, a complementary RNA copy of a DNA sequence is generated. There are several types of RNA including mRNA and rRNA. mRNA is translated by ribosomes into proteins, the functional molecules that carry out most tasks in cells. Various techniques are used in molecular biology like PCR, gel electrophoresis, and blotting to study these biomolecules.
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.
This document discusses variable number tandem repeats (VNTRs), specifically microsatellites and minisatellites. It defines VNTRs as sequences with a variable number of tandem repeats of short DNA motifs. Microsatellites have repeat units of 1-10 bp while minisatellites have larger repeat units of 9-65 bp. Minisatellites can be detected using Southern blots with probes targeting the core repeat sequence, while microsatellites are detected using PCR. VNTRs are highly polymorphic due to variations in the number of repeats, making them useful for applications like forensic analysis, genetic mapping, and varietal identification.
The chain-termination method developed by Frederick Sanger and coworkers in 1977. This method used fewer toxic chemicals and lower amounts of radioactivity than the Maxam and Gilbert method. Because of its comparative ease, the Sanger method was soon automated and was the method used in the first generation of DNA sequencers.
Types of Restriction Endonuclease enzymesNishanth S
Restriction enzymes are produced by bacterial cells to protect themselves from foreign DNA. There are three main activities of restriction enzymes: recognition, digestion, and modification. Restriction enzymes are classified into three groups based on their source and biochemical activity: isoschizomers which have the same recognition and cleavage sites, neoschizomers which have the same recognition site but different cleavage sites, and isocaudomers which have different recognition sites but the same cleavage sites.
Dna replication and enzymes involved in dna replicationNarayan Prahlad
DNA replication is the process by which DNA copies itself. It requires DNA polymerase enzymes, primers, and deoxynucleotide triphosphates. DNA polymerase adds nucleotides to the 3' end of the primer according to the DNA template. Replication occurs through the coordinated action of helicase, DNA polymerase, primase, ligase, and other proteins. DNA polymerase proofreads newly synthesized DNA to ensure high fidelity. The coordinated actions of these enzymes and proteins precisely duplicate the genome during semi-conservative replication.
This document summarizes three main next generation sequencing technologies: Roche/454FLX pyrosequencing, Illumina/Solexa sequencing by synthesis, and Applied Biosystems SOLiD sequencing by ligation. Pyrosequencing works by detecting pyrophosphate released during DNA polymerization, producing light signals to determine the sequence. Roche/454FLX amplifies DNA fragments on beads in emulsions and sequences in picotiter plates. Illumina attaches DNA fragments to a flow cell for bridge amplification and sequencing by synthesis. Applied Biosystems SOLiD performs sequencing by ligation, determining sequences through sequential ligation of oligos.
The document summarizes the application of recombinant DNA technology in forensic science. It discusses how DNA analysis using techniques like PCR, STR, RFLP, and mtDNA can be used to analyze biological evidence from crime scenes to identify individuals. DNA profiling has become an important tool in forensic investigations to solve crimes and legal cases involving issues like identification, paternity testing, and exoneration of suspects. The document also provides examples of different biological materials that can be tested and discusses how DNA databases like CODIS are used to match crime scene evidence to known offender profiles.
This document is a biochemistry assignment submitted by Nibedita Ayan, an MBBS student at Xiamen Medical College, China under the guidance of Dr. A. K. M. Arif Uddin Ahmed. The assignment discusses nucleic acids, their discovery, structure, roles, and impacts. It covers topics such as nucleic acids carrying hereditary information and acting as carriers of genes, DNA and RNA having different but important roles, the central dogma of biology regarding DNA transcription and protein synthesis, DNA replication enabling species continuation, and various aberrations in nucleic acids like mutations, which can impact evolution, cancer development, and more.
DNA sequencing determines the precise order of nucleotides in a DNA fragment. There are several methods for DNA sequencing, including the chain termination method developed by Sanger, and the Maxam-Gilbert chemical cleavage method. Next generation sequencing is now used, which allows high-throughput sequencing of entire genomes quickly and accurately using automated methods. DNA sequencing has many applications, such as identifying disease-causing genes and mutations.
DNA, or deoxyribonucleic acid, is the hereditary material found in humans and most organisms that contains the genetic instructions used in the development and functioning of living beings. DNA is located in the cell nucleus for eukaryotic cells like humans, but in the cytoplasm for prokaryotic cells like bacteria. DNA is composed of nucleotides containing phosphate, sugar, and nitrogen bases that form the signature double helix structure. The sequence of these bases determines the organism's traits and functions. DNA analysis has various important applications in fields like genetics, medicine, agriculture, law, and archaeology.
DNA is highly compacted in cells through various levels of supercoiling and chromatin structure. At the most basic level, DNA wraps around histone proteins to form nucleosomes, introducing negative supercoiling. Nucleosomes are then packed into a beads-on-a-string structure and further compacted into the 30nm fiber. Additional folding compacts the DNA over 10,000-fold into the final chromosomes. The two main types of supercoiling that facilitate compaction are plectonemic and solenoidal, with solenoidal supercoiling allowing the greatest degree of compaction and found in chromatin.
DNA fingerprinting is a technique used for identification by extracting and analyzing the base pair pattern of an individual's DNA. It involves isolating DNA from a sample, cutting the DNA into fragments using restriction enzymes, and comparing the fragment patterns on a gel to identify individuals. The main applications of DNA fingerprinting are in solving criminal cases by matching DNA evidence to suspects, diagnosing inherited diseases, and determining biological relationships in areas like paternity testing.
1) DNA fingerprinting is a technique used to identify individuals by their unique DNA patterns. It analyzes Variable Number Tandem Repeats (VNTRs) in DNA, which vary between people.
2) The Southern blot technique is used to detect and analyze VNTRs. It involves extracting DNA from a sample, cutting it, separating fragments by size, and probing for specific VNTRs.
3) PCR (polymerase chain reaction) is used to amplify small DNA samples. It heats and cools DNA in cycles to make billions of copies of specific DNA regions for analysis.
This document summarizes various mechanisms of DNA repair. It discusses sources of DNA damage including exogenous sources like radiation and chemicals, and endogenous sources like oxidation. It describes different types of DNA damage such as oxidation, deamination, alkylation, and dimerization. The key DNA repair mechanisms discussed are direct reversal, base excision repair, nucleotide excision repair, mismatch repair, and double-strand break repair. The document emphasizes that without proper DNA repair, damage can lead to genomic instability and disease.
DNA and RNA are nucleic acids that are essential for life. DNA contains the genetic instructions used in the development and functioning of all living organisms. It is a double-stranded molecule found in the nucleus of cells. RNA is a single-stranded molecule that helps carry out the instructions specified by DNA, such as synthesizing proteins. The four bases found in DNA are adenine, guanine, cytosine, and thymine, while RNA contains adenine, guanine, cytosine, and uracil. Watson and Crick discovered that DNA has a double helix structure in 1951. Their model showed how the bases on each strand are paired through hydrogen bonding in a complementary way.
RNASeq - Analysis Pipeline for Differential ExpressionJatinder Singh
RNA-Seq is a technique that uses next generation sequencing to sequence RNA transcripts and quantify gene expression levels. It can be used to estimate transcript abundance, detect alternative splicing, and compare gene expression profiles between healthy and diseased tissue. Computational challenges include read mapping due to exon-exon junctions and normalization of read counts. Key steps in RNA-Seq analysis include read mapping, transcript assembly, counting and normalizing reads, and detecting differentially expressed genes.
Basics of molecular biology tools and techniquesBOTANYWith
The key players in molecular biology are DNA, RNA, and proteins. DNA is the blueprint stored in the genome that contains the genetic instructions. It is replicated for cell division. During transcription, a complementary RNA copy of a DNA sequence is generated. There are several types of RNA including mRNA and rRNA. mRNA is translated by ribosomes into proteins, the functional molecules that carry out most tasks in cells. Various techniques are used in molecular biology like PCR, gel electrophoresis, and blotting to study these biomolecules.
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.
أثناء المراحل الأولى سادت الأوساط العلمية مفهوم أن الجين قطعه واحده لها جزئ من (DNA) وهى المادة الكيميائية للوراثة
هذه الصورة المبسطة تغيرت تغيرا كاملا
عندما اكتشف ريتشارد روبرت وفليب شارب عام 1977
بصوره مستقلة أن الجين
يمكن أن يتواجد في صوره قطع عديدة منفصلة
استخدما نظام نموذج بيولوجي
3. مادة الوراثة الحموض النووية تتكون الكروموسومات في الخلايا الحية من مادتين اساسيتين هما : * الحمض النووي DNA : الذي يشكل المادة الوراثية ومجموعة من البروتينات تعرف بالهستونات والتي يقوم شريط بالالتفاف حولها بشكل متكرر مشكلا النيوكليوسوم فيؤدي الىتكثيف المادة الوراثية مما يساعد على تخزينها في حيز صغير في داخل الانوية الحمض RNA : يلعب كل منها دورا مهما اساسيا في ترجمة المعلومات الوراثية في جزيء الى بروتينات عدة تقوم بأداء كافة الوظائف اللازمة لحياء الكائنات الحية .
4. تكثيف ( DNA) داخل الكروموسومات كروماتيدان لفة واحدة الشكل الوردي للكروماتين ( يحتوي 6 لوالب الشكل اللولبي للكروماتين DNA ملتف حول الهستونات ( نيوكليوسوم ) سسلستا DNA تلتفان بشكل حلزوني
6. تمكن العالمان جيمس واطسون وفرنسيس كريك في منتصف القرن الماضي من اكتشاف الشكل الاساسي للحمض النووي الذي ادي لاحقا الى التعرف على الكثير من المعلومات حول كيفية قيامه بحفظ وتخزين المعلومات وكيفية انتقالها من جيل الى اخر اكتشاف الحموض النووية
7. تتكون الحموض النووية من سلاسل من وحدات بنائية فدعى النيوكليوتيدات ويتألف كل تيوكليوتيد من ثلاثة مكونات اساسية 1- جزي سكر خماسي 1- مجموعة فوسفات قاعدة نيتروجينية والقواعد التيتروجينية نوعان 1- بيورينات وتشمل على قاعدتين هما : ادينين و غوانين وتتالف مل منهما من حلقتين 2- بيرودينات : وتستمل على ثلاث قواعد هي : ثايمين وسايتوسين ويختلف اركيب النيوكليوتيدات عن بعضها البعض بناء عن : * نوع القاعدة النيتروجينية * وجزيء السكر الموجود : رايبوز او رايبوز منقوص الاكسجين التركيب الكيمائي للحموض النووية
8. قواعد نتيروجينية قاعدة نتيروجينية قاعدة نتيروجينية سكر رايبوز سكر رايبوز منقوص الاكسجين
9. غوانين ( G ) يوراسيل U ثايمينT سايتوسينC أدينين A بيورينات بيرمدينات القواعد التيتروجينية
10. الحمض النووي DNA اختصارا " الحمض النووي الرايبوزي منقوص الاكسجين " ويتالف من سسلسلتين من النيوكليوتيدات تلتفان حول بعضهما البعض بشكل حلزوني ويلاحظ من الشكل ان القاعدة النيتروجينية ادينين A في احدى السلاسل تكون متقابلة مع القاعدة النيتروجينية ثايمين T في السلسلة الثانية وترتبط معها برابطتين من الروابط الهيدروجينية بينما تكون القاعدة التيتروجينية غوانين G متقابلة مع القاعدة التيتروجينية سايتوسين C وترتبط معها بثلاث روابط هيدروجينية . تتكون سلسلة الحمض النووي DNA من ارتباط مجموعة الفوسفات في كل نيوكليوتيد مع سكر الرايبوزي منقوص الاكسجين في النيوكليوتيد التالي وتشكل سلسلة القواعد النيتروجينية في جزي DNA مخزون المعلومات الوراثية ويسمى ترتيبها بالشيفرة الوراثية التي تميز كافة الكائنات الحية عن بعضها البعض
13. المفهوم اختصارا " الحمض النووي الرايبوزي " ويتالف من سلسلة واحدة فقط من النيوكلوتيدات التي تربط بعضها مع بعض بنفس الطريقة التي ترتبط بها في جزيء DNA ويختلف عن جزي ء في احتوائه على القاعدة النيتروجينية يوراسيل بدلا من الثايمين انواع الحمض النووي 1- mRNA الرسول يقوم بتقل الشيفرة الوراثية من الجينات في النواة الي الرايبوسومات ليتم تصنيع البروتينات المختلفة داخل السيتوبلازم 2- tRNA الناقل : يقوم بنقل الحموض الامينية في السيتوسول الى الرايبوسومات لاستخدامها في عملية بناء البرونينات 3- rRNA الرايبوسومي : يستخدم في اناج الرايبوسومات في الانوية داخل نواة الخلية الحمض النووي RNA
14. إن مقدرة الخلايا الحية في الحفاظ على درجة عالية من الدقة في الاستمرار في وظائفها من جيل الى جيل تعتمد على قدرتها على مضاعفة المعلومات الوراثية المخزون في جزيء DNA المكون للكروموسومات ويكون ذلك في الطور البيني قبيل عملية الانقسام وإنتاج خلايا جديدة الشروط الواجبة لتضاعف جزي DNA : 1- جزي DNA الذي تلزم مضاعفته ليتم انتاج جزيئات جديدة تحمل نفس المعلومات الوراثية 2- كميات كافية من النيوكلوتيدات الاربعة المختلفة التي تدخل في تركيبه ( T , C , G , A ) . 3- إنزيم التضاعف ( انزيم البلمرة DNA ) اضافة الى بعض الانزيمات والبروتينات الاخرى اللازمة لإتمام العملية . آلية تضاعف الحمض النووي DNA
15. الخطوات التي يتم بها التضاعف : 1- تنفصل سلسلتي جزيء DNA بعضها عن بعض بشكل تدريجي نتيجة تكسر الروابط الهيدروجينية التي تربط القواعد النيتروجينية ببعضها فتتحول الى سلاسل احادية بدءا من نقطة محددة وينشطر بشكل طولي حتى نهاية السلسلة -2 يرتبط انزيم التضاعف بالسلسلة الاحادية ويقوم بوضع النيوكليوتيدات الموجودة في السائل النووي - الواحدة تلو الاخرى بشكل متمم حسب ترتيب القواعد النيتروجينية الموجودة في سلسلة جزيء DNA الذي يتم تضاعفه بحيث يتم وضع نيوكليوتيد مقابل نيوكليوتيد ونيوكليوتيد مقابل نيوكليوتيد وتستمر هذه العملية بالتحرك انزيم التضاعف من نقطة البدء حتى نهاية السلسلة 3- تتم عملية تضاعف سلسلتي جزي DNA في وقت واحد وفي نفس السرعة فينتج عن هذه العملية جزيئين كاملان DNA من يحتوي كل منهما على سلسلة قديمة وأخرى جديدة . 4- بعدالانتهاء من هذه العملية تقوم بروتينات الهستونات الاصلية والجديدة بالارتباط جميعها بجزيء DNA لتكوين الكروموسومات وتكثيفها داخل النواة
22. يؤدي حدوث اي خطا في ترتيب او تركيب القواعد النيتروجينة في جزي DNA الى تغير المعلومات الوراثية وينتج عن ذلك ما يعرف بالطفرة كما يؤدي هذا التغيير الى في الخلايا الجسدية الى خلل لدى الفرد الذي حدث له ذلك التغيير وفي حالة حصول هذا التغير في الخلايا الجنسية يصبح بإمكان الفرد نقل هذه الطفرة من جيل الى جيل مما يؤدي الى ظهور الامراض الوراثية ويمكن حدوث هذه الطفرات نتيجة تعرض الخلايا لنوعين من العوامل : 1- عوامل داخلية : اثناء عملية التضاعف يقوم انزيم التضاعف بوضع النيوكليوتيدات في غير موضعا الصحيح وتنتج الطفرة عند عدم قدرة الخلايا على اصلاح كافي الاخطاء الناتجة عن ذلك . 2- عوامل خارجية : الاشعاعات المختلفة وبعض الكيماويات او بعض انواع الفيروسات تؤدي الى احداث تغيير في التركيب القواعد النيتروجينية لجزيء وتكمن خطورة هذه الطفرات عند حصولها للجينات الموجودة على الكروموسومات مما قد يؤدي الى التأثير على عملها او وقفها تماما فينتج عن ذلك حدوث الاختلال في الوظائف المرتبطة في هذه الجينات وظهور العديد من الامراض . الطفرة
