1. Why do we have two copies of most of our genes’ sequences and most of the non-gene sequences in our DNA as well? If you tested polymorphic sequences on the X chromosome and Y chromosomes, how many alleles would a man have for each of these sequences? Why?

2. Why is it that, if two people have different alleles of a gene, they may have different versions of any phenotypic traits that gene’s protein influences?

3A. What does the polymerase chain reaction do? How has this enabled forensic DNA analysts to perform investigations they could not perform before PCR was invented?

3B. If the 4 allele of a tetranucleotide repeat STR produced a 200 bp long PCR product, how long a PCR product will the 9 allele of that STR produce?

4. Imagine you have a match between the DNA profiles of the defendant and the crime scene evidence, with the following DNA profile, and the following allele frequencies in the relevant database. What is the RMP for this DNA match? Show all your work.

5-6. Paternity Testing Questions

A woman is pregnant and wants to identify the father of her child. She admits “going wild”

one night with a group of her male friends, and doesn’t remember some of the details of that night. She believes there are three men who might be the father.

The table below gives you everyone’s genotypes for these 6 genes—i.e., the table tells you which alleles the person has for each of these 6 genes. Each genotype has two alleles in it, because we all have two copies of each of these 6 genes

Question 5: Do the data implicate any of these three men as the true father of the child? Give me an explanation of why you do or do not identify Man 1, Man 2 and Man 3 as the father of the child. Give a specific answer for each man, identifying the genes whose data do not implicate any man who is not implicated as the true father of the child. Assume there have not been any mutations in the alleles the child inherited from either the mother or the father.

Question 6: Based on the genetic data and the information in the writeup, how would you expand the investigation in your effort to identify the true father of this child?

Question 7: Why must a company that performs DNA phenotyping analyses report confidence levels for their conclusions about the phenotypic characteristics of the person whose DNA was analyzed, rather than definitive statements about his/her phenotypic traits?

Question 8: A woman has identified several men as the potential father of her child. One of them has been implicated by a three-STR test. The table below shows the genotypes for the child, the mother and the implicated man, as well as the allele frequencies for the alleles the child inherited from the father.

8A. Please calculate the probability of paternity, given the allele frequencies below. Show all your work.

8B. Would this man be declared the true father of the child?