1. Federal University of Technology, Owerri
(FUTO)
School of Biological sciences (SOBS)
Department of Biochemistry
Seminar Presentation
Topic: DNAAnalysis as Evidence in Criminal Justice
By: Mbamalu Anthony Ugochukwu
Reg no: 20181089595
2. PRESENTATION OUTLINE
•Overview of DNA Molecules
•Structures and Features of DNA Molecules
•DNA Replication
•DNA as Information Store
•Analysis of DNA Evidence
•Steps in Analyzing DNA Evidence
•Types of DNA Evidence Analysis
•DNA Evidence in Criminal Justice System
•Issues with DNA Evidence in Criminal Justice
System
•Conclusion
3. OVERVIEW OF DNA
MOLECULES
• DNA, or deoxyribonucleic acid, is the genetic
material found in all living organisms. It carries the
instructions for building and maintaining all the
cells in our bodies, and it determines many of our
characteristics.
• DNA is the hereditary material found in all living
organisms. It's made up of two strands that are
coiled around each other to form a double helix.
Each strand is made up of a sugar (deoxyribose), a
phosphate group, and one of four different
nitrogen-containing bases: adenine (A), guanine
(G), cytosine (C), and thymine (T). The order of
these bases in the DNA sequence is what
determines an organism's traits and characteristics.
4. STRUCTURE OF DNA
MOLECULES
• Although sometimes called "the molecule of heredity," pieces of
DNA as people typically think of them are not single molecules.
Rather, they are pairs of molecules, which entwine like vines to form
a double helix.
• Each vine-like molecule is a strand of DNA: a chemically linked
chain of nucleotides, each of which consists of a sugar, a phosphate
and one of four kinds of aromatic "bases“
• In a DNA double helix, two polynucleotide strands come together
through complementary pairing of the bases, which occurs by
hydrogen bonding
• Each base forms hydrogen bonds readily to only one other -- A to T
and C to G -- so that the identity of the base on one strand dictates
what base must face it on the opposing strand. Thus the entire
nucleotide sequence of each strand is complementary to that of the
other, and when separated, each may act as a template with which to
replicate the other
6. DNA REPLICATION
• Before DNA duplicates, it is divided into new daughter
cells through either mitosis or meiosis, biomolecules
and organelles must be copied to be distributed among
the cells
• There are four steps in DNA replication, they are;
Replication Fork Formation; Primer Binding;
Elongation; and Termination.
• DNA replication would not occur without enzymes that
catalyze various steps in the process. They include;
DNA helicase; DNA primase; DNA polymerase; DNA
Gyrase; Exonucleases; and DNA Ligase.
7. DNAAS AN INFORMTION STORE
• DNA is often called the blueprint of life because it stores all the information a
cell needs to function. This information is encoded in the sequence of
nucleotides, which are the building blocks of DNA.
• DNA is considered the genetic material because it carries the genetic
information that is passed from one generation to the next. It also plays a role
in determining an organism's characteristics. Every cell in our bodies contains
DNA, which is found in the nucleus of the cell. This DNA contains the
instructions for making proteins, which are responsible for carrying out the
functions of the cell. The sequence of nucleotides in DNA is what makes each
organism unique. Even though we all share the same basic set of genes, the
order of those genes and the way they are expressed can be very different
from person to person.
• DNA stores information by encoding it in the sequence of nucleotides. Each
three-nucleotide sequence, called a codon, encodes a specific amino acid.
These amino acids are the building blocks of proteins, so the sequence of
nucleotides in DNA can be translated into the sequence of amino acids in a
protein. This process is called translation. In this way, DNA stores
information in the form of a code, which can be used to make proteins that
carry out specific functions in the cell.
8. ANALYSIS OF DNA EVIDENCE
• DNA is the material on which the genetic
information in living things is stored. And no
two human beings can have the same DNA
profile, except they are identical twins.
• In terms of DNA analysis, there is a variety of
possible sources of DNA evidence. The more
useful sources include blood, semen, vaginal
fluid, nasal secretions and hair with roots.
9. STEPS IN ANALYZING DNA EVIDENCE
• Several basic steps are performed during DNA testing
regardless of the type of test being done. The general
procedure includes:
1. The isolation of the DNA from an evidence sample
containing DNA of unknown origin, and generally at a
later time, the isolation of DNA from a sample (e.g.,
blood) from a known individual
2. The processing of the DNA so that test results may be
obtained
3. The determination of the variations in the DNA test
results (or types), from specific regions of the DNA
4. The comparison and interpretation of the test results from
the unknown and known samples to determine whether
the known individual is not the source of the DNA or is
included as a possible source of the DNA.
10. TYPES OF DNA EVIDENCE ANALYSIS
Polymerase Chain Reaction (PCR)
PCR works by heating and cooling the DNA sample, which causes the DNA
strands to separate. Then, short pieces of DNA called primers bind to the
regions of interest. The DNA polymerase enzyme then extends the
primers, copying the DNA. This process is repeated many times, resulting
in millions of copies of the target DNA region. This allows for more
accurate and sensitive DNA typing.
Short Tandem Repeat (STR) Analysis
STR, or short tandem repeat, is a type of marker used in DNA typing. STRs
are regions of DNA that have a repeating sequence of nucleotides, like A-
C-T-C-T-C-T-C-T. The number of repeats varies between individuals, so the
length of the STR region is used to identify individuals. This variation in
STR length is what makes STRs so useful for DNA typing. Since there are
thousands of STRs in the human genome, a small number of them can be
used to distinguish between individuals. This makes STR analysis a
powerful tool for forensic science and other applications.
11. TYPES OF DNA EVIDENCE ANALYSIS
Y-Chromosome Analysis
Y-chromosome analysis is a type of DNA typing that uses STRs on the Y-
chromosome. The Y-chromosome is unique because it's passed from father to
son, so it's a good tool for studying male-lineage relationships. The Y-
chromosome also has a lower rate of mutation than other regions of DNA,
which makes it useful for studying relationships between individuals who are
more distantly related. Y-chromosome analysis has been used to study the
ancestry of populations, track the spread of disease, and identify victims of
crimes.
Mitochondrial Analysis
Mitochondrial DNA (mtDNA) analysis is a type of DNA typing that uses the
DNA from mitochondria. Unlike nuclear DNA, which is inherited from both
parents, mtDNA is only inherited from the mother. This makes mtDNA analysis
a useful tool for studying maternal-lineage relationships. Additionally, mtDNA
is often more easily preserved than nuclear DNA, making it a good tool for
analyzing old or degraded DNA samples. It's also used in forensics, evolutionary
studies, and the study of mitochondrial diseases. Since mtDNA has a relatively
slow mutation rate, it's especially useful for studying ancient populations.
12. DNAAS EVIDENCE IN CRIMINAL
JUSTICE SYSTEM
• The DNA typing has significantly contributed to the
administration of justice in various civil as well as
criminal cases.
• The report of DNA is admissible in the court as based on
the belief that it has been made from the experimental
knowledge that DNA is a unique genetic code. It is well
established that no two individuals can possess an
identical DNA profile.
• The DNA evidence has been found to be an effective
tool to establish the identity of a person with a high level
of accuracy and has been referred to as “new gold
standard” in Forensic Science (Sauer et al., 2016).
13. CHALLENGES IN DNAAS EVIDENCE IN
CRIMINAL JUSTICE SYSTEM
• When people think of DNA analysis, they often think
about television shows like NCIS or CSI, which portray
DNA samples coming into a lab and being instantly
analyzed, followed by the pulling up of a picture of the
suspect within minutes. However, the reality is quite
different, and perfect DNA samples are often not
collected from the scene of a crime. Homicide victims
are frequently left exposed to harsh conditions before
they are found, and objects that are used to commit
crimes have often been handled by more than one
person.
• Several issues facing the use of DNA analysis as
evidence in CJs are; Degraded DNA; Low-Template
DNA; MiniSTR Analysis; and DNA Mixtures
14. CONCLUSION
The development of DNA technology has created
new dimensions in criminal investigation. It has also
provided significant corroborative scientific evidence
to the criminal justice system. From Jeffrey’s
discovery of DNA fingerprinting to the development
of PCR of STRs to the formation of DNA databases,
our knowledge of DNA and DNA profiling have
expanded greatly. This paper reviewed the concept
of DNA, the various methods of DNA analysis, the
application of DNA analysis in criminal investigation
and its drawbacks. The future of DNA profiling looks
expansive with the development of newer
instrumentation and techniques.
