DNA profiling for forensic science

1. DNA PROFILING
Submitted by:
Ch. Bandana Devi
16PBT06
I M.Sc. Biotechnology
Women’s Christian College

2. INTRODUCTION
DNA profiling is a technique to identify
individuals by the characteristics of DNA.
• Also called as DNA fingerprinting or DNA
typing.
• Used as a Forensic technique.
• Fist started in 1984.

3. DNA PROFILE
• Set of DNA variations different in unrelated
individuals.
• Unique to individual as fingerprints.
• Current technique uses tandem repeats.
• Short tandem repeats are regions of non-coding
DNA that contains repeats of the same
nucleotide sequence.
• Example GATAGATAGATAGATAGATAGATA
• Found at different genetic loci

4. CREATING DNA PROFILE USING STR
• Collect samples from crime scene.
• Samples may be blood, semen, hair
• DNA can be collected directly from the person
using mouth swab.

5. • The collected DNA are cut into small pieces using
restriction enzymes.
• This generates thousands of small DNA
fragments of different sizes.
• The fragments are then separated using gel
electrophoresis based on the size.

6. COPY THE DNA
• Only small amount of DNA is needed for
Forensic analysis.
• The STRs at each genetic loci are copied many
times using PCR.
• This is done so as to get enough DNA to make
a profile.
• Specific primers are used that attach a
fluorescent tag to the copied STRs.

7. DETREMINE THE SIZE OF STRs
• The size of STRs is determined using genetic
analyser.
• Genetic analyser separates the copied DNA
by gel electrophoresis and detect the
fluorescent dye.

8. LOOKING FOR A MATCH
• The number of times a nucleotide sequence is
repeated in each STR can be calculated from
the size of the STRs.
• This information can be used by the forensic
analyst to determine if a specific fluid sample
comes from a particular person.
• If two DNA profile from different samples are
the same, the chance that the sample come
from different person is low.

9. LOOKING FOR A MATCH
• This provides strong evidence that the sample
have a common source.
• To produce DNA profile, scientists examine STRs
at ten or more genetic loci.

10. DNA PROFILING USING STR

11. APPLICATIONS
• Paternity testing- comparing DNA of offspring
against potential father.
• Forensic investigation- identifying suspects or
victims of a crime-scene DNA.