A sample from a crime scene is genotyped for 4 STR markers located on different chromosomes. The genotypes from a DNA sample collected from blood at the crime scene and from two suspects are given below. The population frequencies of STR alleles at each locus are also given (alleles are designated by the length of the DNA repeat)
MCB10ProblemSet2Fall2016
Crime scene sample:
Marker 1: 102/101 Marker 2: 121/112 Marker 3: 100/100 Marker 4: 132/154
Suspect 1:
Marker 1: 102/101 Marker 2: 121/112 Marker 3: 100/100 Marker 4: 132/154
Suspect 2:
Marker 1: 101/101 Marker 2: 112/112 Marker 3: 100/100 Marker 4: 148/154
Population Allele Frequencies:
Marker 1: f(102)=0.40, f(101)=0.32.
Marker 2: f(121)=0.10, f(112)=0.90.
Marker 3: f(100)=0.97, f(106)=0.03.
Marker 4: f(132)=0.04, f(154)=0.74, f(148)=0.22.
(a) Can either of suspects 1 or 2 be excluded as the perpetrator of the crime based solely on their marker genotypes?
(b) Calculate the probability of a genotype match at the 4 loci for an individual drawn at random from the population for which the allele frequencies have been specified above.