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DNA profiling is a technique that identifies individuals by comparing their DNA profiles, particularly through the analysis of short tandem repeats (STRs). It is widely used in criminal investigations and paternity testing, involving the collection and amplification of DNA samples, followed by fragment analysis. The effectiveness of DNA profiling in forensics relies on matching DNA samples from crime scenes to suspects, while in paternity testing, it verifies biological relationships between parents and children.

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13 views13 pages

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DNA profiling is a technique that identifies individuals by comparing their DNA profiles, particularly through the analysis of short tandem repeats (STRs). It is widely used in criminal investigations and paternity testing, involving the collection and amplification of DNA samples, followed by fragment analysis. The effectiveness of DNA profiling in forensics relies on matching DNA samples from crime scenes to suspects, while in paternity testing, it verifies biological relationships between parents and children.

Uploaded by

tristapc.17
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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The Future of

DNA profiling
DNA forensics:
How DNA has
revolutionized
criminal investigations

2
methods have
3
become faster,
more sensitive, and
more user-friendly
since the first
murderer was
caught with help
from genetic
evidence.
Understanding:
4 • DNA profiling involves comparison of DNA

▹ DNA profiling is a technique by which individuals can


be identified and compared via their respective DNA
profiles

▹ Within the non-coding regions of an individual’s


genome there exists satellite DNA – long stretches of
DNA made up of repeating elements called short
tandem repeats (STRs)
▹ As individuals will likely have different numbers of
Comparative STR Lengths at Two Specific Loci

5
Application:

• Use of DNA profiling in


paternity and forensic
investigations

6
”
Application:
▹
7 DNA profiling is commonly used in criminal investigations (forensics) and
to settle paternity disputes

▹ The procedure involved is common for both:

▹ A DNA sample is collected (e.g. from blood, semen, saliva, etc.) and then
amplified using PCR
▹ Satellite DNA (with STR sequences) are cut with specific restriction
enzymes to generate fragments
▹ Fragment length will differ between individuals due to the variable
length of their short tandem repeats
▹ The fragments are separated using gel electrophoresis and the resulting
profiles are compared
8 Forensic Investigations:
Suspects should be a complete match with the
DNA sample taken from the crime scene if a
conviction is to occur
The number of loci used to generate a unique
profile depends on the size of the population
being compared
• E.g. America (population: ~ 320 million)
uses 13 loci for comparison; Australia
(population: ~ 25 million) uses only 9 loci
9 Paternity Testing:

Children inherit half their chromosomes from


each parent and thus should possess a
combination of parental fragments

In other words, all fragments produced in the


child should also be produced by either the
mother or father
Skill:
• Analysis of examples of DNA profiles
10
Example 1: Forensic Investigation

Compare the DNA collected from the crime scene to determine which of the three suspects
was present (click picture to solve)
Example 2: Paternal Testing

11 Compare the profiles of three men with that of a mother and child to determine
the biological father (click picture to solve)
12

What is the big impact


of the DNA profiling in
Forensic Science?
13

THANK
You!

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