A victim of murder is found to have scrapings containing skin cel...

Question

A victim of murder is found to have scrapings containing skin cells under several of her fingernails. Genetic analysis confirms that the DNA isolated from these cells came from the same individual and does not match the DNA of the victim. The results shown below are for six CODIS STR markers from the crime scene DNA (from under the victim's fingernails and presumed to be the murderer's), and from three suspects (A, B, and C) who have been detained for questioning about the murder.

Do the STR results exclude any of the three suspects? Explain.

Accepted Answer

Welcome back, everyone. Let's look at our next question. What is the minimum number of alleles required to declare a match between two DNA samples in S T R analysis? A one B two C, three, four D four. Well, we're talking about a number of alleys. Each all will have a number of repeats of a specific DNA sequence. And when we think about alleys, let's think about any gene. We're talking about how many alleys will an individual have? Well, each individual has two alleys of any particular gene. Since there are two of each chromosome, you have one all on each chromosome, one inherited from each parent. So the minimum to declare a match would be choice B two, all. You're looking at both chromosomes, the number of repeats on each chromosome because you'll have different numbers of repeats on each one unless your mother and father happen to have the same number of repeats at that low side. So two would be the minimum number of alleles. Now, if you're doing a forensic analysis, you need this to be a legal proof, you're not just going to go on two alleles at one low to compare your samples and see if you have a match, you would look at multiple low to get a really, really high degree of likelihood that there's a match. But when we're thinking about a minimum number, we would look at choice B two so that you have the two chromosomes that you're looking at. See you in the next video.

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