1. Paternity Testing Biology Alliance May 13

3. A pair of homologous chromosomes, (one from mom, one from dad) Gene unit of DNA information about a trait passed from parents to offspring specific location on a chromosome Fig. 8-1, p.113 Alleles – different versions of a gene Human Chromosomes Humans have 23 pairs of homologous chromosomes

4. Polymerase Chain Reaction (PCR) Developed in 1983 by Kary Mullis Awarded Nobel Prize in 1993

5. PCR Basics Isolate and mass produce a particular DNA fragment – Template DNA – Polymerase – enzyme that replicates DNA, matches complementary bases – Primers – 10-30 base pairs long, complementary to ends of fragment

6. PCR Basics Isolate and mass produce a particular DNA fragment – Denature – Anneal – Extend

7. Short Tandem Repeats Short regions of DNA that differ substantially among people – TCAT Each person carries a unique combination of repeats

8. (a)DNA and dye are loaded in a well on a gel, and an electric field is placed across the gel. (b)DNA fragments move through the gel, shorter fragments faster than longer fragments. Electrode Gel Well DNA samples from PCR Direction of electric field

9. Applications? Implicating a crime suspect, acquitting the wrongly convicted Paternity Identifying the deceased

11. Obtaining DNA Any biological material – Body tissues – Body fluids – Hair follicles – Dried material

12. Power of Discrimination Ability to discriminate between different individuals The larger the number of loci used, the more powerful the ability to discriminate

15. CODIS COmbined DNA Index System database of DNA obtained from crime scenes and convicted violent offenders 13 loci

16. Alleles

17. Paternity Index Likelihood ratio: X/Y X = chance that the AF could transmit the obligate allele Y = chance that some other man of the same race could have transmitted the allele X = 1 if father is homozygous X = 0.5 if father is heterozygous D8 hypothetical example: 13 is obligate allele, frequency of 9 = 0.308 PI = 0.5/0.308 = 1.62

18. Paternity Index

19. Combined Paternity Index (CPI) All PI multiplied by each other 27,746

20. Probability of Paternity CPI CPI + (1-prior probability) 27,746 27,746 + (1-0.5) x 100 x 100 = 99.998%