Polymerase chain reaction (PCR) is used in several forensic DNA typing methods to amplify specific regions of DNA. These include STR analysis of microsatellite repeats, SNP analysis of single nucleotide variations, mtDNA analysis for maternal lineage, and Y-chromosome analysis for paternal lineage. PCR amplifies targeted regions which are then analyzed using techniques like capillary electrophoresis to develop a DNA profile that can identify individuals or determine ancestry.

1. Forensic Serology & DNA Typing…
M.PHOOL BADSHAH

2. Lecture-8
Forensic DNA Typing Methods

3. Introduction
• Polymerase Chain Reaction (PCR) is a basic procedure in forensic
DNA typing, which involves generating a distinct profile for
individual identification of particular sections of DNA to be studied
using a range of techniques.
PCR is often employed in the following methods:
1-PCR Technique
2-STR Analysis
3-SNPAnalysis
4-mtDNA Analysis
5-Y-Chromosome Analysis:

4. 1- Polymerase Chain Reaction (PCR):
 A specific DNA region is amplified via PCR in order to be examined.
 How PCR Works: Short extracted DNA segments, such as minisatellite
(VNTRs) or microsatellite (STRs), are the target audience for
amplification. The amplified DNA can then be analyzed to establish a DNA
profile.
2- Analysis of Microsatellite (STR):
 Purpose: STR analysis because of the significant individual diversity of
STR regions, STR analysis is a frequently used approach in forensic DNA
typing.
 How it Works: PCR is used to target specific loci containing short
repeating DNA sequences. The resulting PCR products are separated using
capillary electrophoresis, and each individual's DNA profile is created
based on the distinct pattern of each repetition at each locus.

5. 3- Analysis of Single Nucleotide Polymorphisms (SNPs):
 Purpose: We examine variations in individual nucleotides and analyze
them to find ancestry and do kinship studies.
 How it Works: By utilizing PCR to target specific SNPs, variations at
those DNA loci can be found by analyzing the resulting DNA fragments.
4- Sequencing of mitochondrial DNA (mtDNA):
 Purpose: MtDNA is used in cases involving maternal lineage or in the
identification of remains, and for further examination when nuclear DNA is
damaged or unavailable.
 How it Works: A portion of the genome found in mitochondria is
amplified using PCR and then sequenced. The sequence data can be
compared to reference databases in order to identify particular individuals.

6. 5- Y-Chromosome-based Analysis:
 Purpose: Tracing paternal lineage via Y-chromosome analysis is
particularly useful when the biological sample is totally male.
 How it Works: PCR is used to amplify certain regions of the Y
chromosome, and the resulting DNA fragments are analyzed to determine
haplotypes and identify male donors.
6- Capillary Electrophoresis:
 Purpose: DNA fragments are sorted and examined using this procedure
based on their size.
 How it Works: Capillaries filled with polymer are then filled with DNA
fragments amplified by PCR, such as STRs. The pieces must pass through
the capillary in order to be forced to do so by an electric field. Using size-
based separation, DNA profiles can be produced.