Outline for today

1
Outline for today

• Pour gels
• SIRS Pre-lab lecture
• Load and run gels
• Forensic analysis of result

2
PCR Review

• PCR DNA replication in a tube
• Why is PCR important in forensics?
• Able to amplify from very small quantities
• Able to target specific areas of genome

3
PCR in Forensics

• PCR analysis in forensics involves the targeting
  and amplification of 13 Short Tandem Repeat
  regions (STRs)
• Each of the 13 loci are characterized by a short
  sequence of DNA that is repeated various numbers
  of times

4
Why the 13 Loci?

• The 13 loci were chosen for several reasons
• Distance from each other on genome assures
  independent assortment
• High number of alleles present at each locus
  assures variability between individuals
• No relation of these loci to phenotypic traits

5
STR analysis TH01 Example

• TH01
• Located on chromosome 11
• Repeated segments of TCAT
• Over 20 possible alleles (each have a different
  number of TCAT repeats in a row)

CCCTCATTCATTCATTCATTCATTCA
1 2 3 4
5
6
STR analysis TH01 Example
Copy from Mother
CCCTCATTCATTCATTCATTCATTCA
1 2 3 4
5
Copy from Father
1 2 3 4
5 6
CCCTCATTCATTCATTCATTCATTCATTCA

• This individual would be typed as a 5,6

7
Results of the PCR in a gel
20 15 10

• Allelic ladder indicates the sizes of known
  alleles
• According to this gel
• S1 9,12
• S2 11,16
• This procedure is repeated for each of the 13
  loci after all alleles are visualized, a full
  profile is compiled

8
Running a full profile gel FMBIO II
9
STR Analysis

• Inclusion the Suspects profile is consistent
  with the evidence profile (it cannot be excluded)
• Exclusion the Suspects profile is not
  consistent with the evidence profile

10
Sample Gels
AL CS 1 2 3
4
15 10 7
5
4
3
2
1
Which suspects are excluded? Included? What is
going on in Lane 3?
11
Sample Gels - Paternity
AL F M 1 2
3
15 10 7
5
4
3
2
1
Are all of these children (1-3) included as
potential offspring of this mother (M) and father
(F)?