Question

1. When there is a match between a forensic DNA sample collected at a crime scene and DNA subpoenaed from a suspect, the genotype frequency can be interpreted in two ways. In one sense, it is the probability of finding that specific genotype in the population. In another sense it is the probability that the match is due to chance.

2. How does the results from the most common alleles in the different populations affect the application of using these results for forensic analysis? (4.5 pts)

3. For identification purposes, crime laboratories have settled on a panel of 13 highly variable short tandem repeat (STR) loci, which are amplified together in a single PCR reaction. Since the loci are located on different chromosomes they are thought to be unlinked – that is they are inherited independently of each other. Thus, the probability of inheriting a given set of alleles at the 13 loci what is the product of their individual probabilities of sample of only six loci is listed below.

	Allele 1	Allele 2
Locus A	0.25	0.15
Locus B	0.10	0.15
Locus C	0.05	0.10
Locus D	0.05	0.20
Locus E	0.20	homozygote
Locus F	0.15	0.05

Remember that Hardy Weinberg can be expanded to calculate the genotype frequencies with any number of alleles. For instance, for three alleles the frequencies can be calculated from the following: p² + q² + r² + 2pq + 2qr + 2qr = 1

1. Assuming Weinberg equilibrium calculate the probability of the following genotype for all six loci occurring (A – F) using the data from the table above. (4.5 pts)

2. What does this show you about the power of using multiple loci? (4.5 pts)

6. The table below shows the frequencies of the PMCT118 alleles in several different human p Allele Frequency (n = number of alleles typed) Allele Allele U.S. Caucasians In 200) African Americans (n214) Hispanic Americans (n=210) U.S. Caucasians (n = 200) 0.008 0.08 African Americans ( 214) 0.008 0.048 0.005 0.055 0.058 0.048 0.013 0.003 0238 0.098 0.003 0101 0.003 0.033 0.04 0.018 0.115 Hispanic Americans in 210) 0.003 0.003 0.013 0.263 0.005 0.02 0.025 0.028 0.003 0.318 0.055 0.01 0.008 0.05 0.055 0.003 0.003 0.005 0.03 0.008 0.008 0.003 0.005 0.348 0.04 0.015 0.013 0.063 0.053 0.088 0.023 0.193 0.023 0.008 0.013 0.153 0.055 40 0.003 0.003 0.01 >41 0.005 0.01 0.005 Table adapted from: Klitz W. Reynolds R., Chen J. Erlich HA. (2000). Analysis of genotype frequencies and interlocus association for the PM, DOAT, and PMCT118 loc in four populations. Forensic Sd, 45(5):1009-15. f we assume that each population is in Hardy-Weinberg equilibrium then the following formul calculate genotype frequencies in a population with two alleles: p? + 2pq + q* = 1. "p" is the frequ llele and"q" is the frequency for the other allele. "2" is the expected frequency of homozygotes llele and "2pq" is the expected frequency of heterozygotes and q?" is the expected frequency of for the second allele. It is therefore possible to calculate the expected frequency of a genotype fre requencies, such that the frequency of homozygotes is the square of the frequency of the homozy he frequency is two times the product of the frequency of the alleles for heterozygotes. a. Using the allele frequency data from the table above, calculate the expected frequency genotype in U.S. Caucasians. (4.5 pts)

Answer 1

a) probability of loci A-F is 0.25+0.10+0.05+0.05+0.20+0.15/6 = 0.675

a) the power of using multiple loci frequently have more than two alleles providing increased genetic resolution per locus.it is limit only by genome size and technology

a)