Question

The U.S. Department of Justice has established a database that catalogs PCR amplification products from short tandem repeats of the Y chromosome (Y-STRs) in humans. The database contains polymorphisms of five U.S. ethnic groups (African-Americans, European Americans, Hispanics, Native Americans, and Asian-Americans) as well as the worldwide population.

Given that STRs are repeats of varying lengths, for example (TCTG)₉₋₁₇ or (TAT)₆₋₁₄, explain how PCR could reveal differences (polymorphisms) among individuals. How could the Department of Justice make use of those differences?

Accepted Answer

Hi, welcome back, let's look at the next problem, polymerase chain reactions can be used to reveal differences or polymorphisms among individuals by. Well let's recall that pcR is that technique that's used to amplify specific sections of D. N. A. So you have probes that specify I want the the DNA between these two probes and you can make many many many many copies from a small sample sort of allowing you to look at that sequence. So when we look at our answer choices um Again we're looking so how would being able to amplify a specific region help us to reveal differences or polymorphisms among individuals? Well, one of the main areas we see these differences is in regions that have these many short tandem repeats and these very quite a bit among individuals. So if you look at the sequences how many repeats there are. Um you can distinguish between individual people. So with that in mind let's look at our answer choices. Keeping in mind that we do have a choice D all of the above. So we may have more than one correct answer choice A says analyzing the DNA sequence of the str region. Well this is correct. When you amplify that signal and make many many copies of it. You could then sequence your piece that you copied and see what the specific DNA sequences of that str region and that would allow you um to see differences in different samples. Joyce B says analyzing the size of the amplified pcR product of the str region. And this is another correct answer because it's a short term repeat or excuse me, short tandem repeat region. That means that the more repeat you have, the bigger that region will be, the fewer, the smaller. So just by looking at the size of the region you amplified, um you could see differences among individuals. Then choi C. Says comparing the str profiles of multiple individuals. Well this is also correct. You could take multiple samples, uh use the same probes on each sample, run a pcr and you will end up with amplified sequences from the different individuals that you can compare to each other. So as we can see our correct answer choice here is D all of the above. So again, chain reactions can be used to reveal differences polymorphisms among individuals by choice D. All of the above. See you in the next video.

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