Question

A family consisting of a mother (I-1), a father (I-2), and three children (II-1, II-2, and II-3) are genotyped by PCR for a region of an autosome containing repeats of a 10-bp sequence. The mother carries 16 repeats on one chromosome and 21 on the homologous chromosome. The father carries repeat numbers of 18 and 26.

What genetic term best describes the pattern of inheritance of this DNA marker? Explain your choice.

Accepted Answer

Hi, everybody. Welcome back. Here's our next question. DNA based markers have many advantages over genetic markers. Which of the following advantages of DNA markers is incorrect choice. A, they're highly heritable B, they are easy to assay c environment dependent expression or D they are pheno typically neutral. Well, first, we have to think about what is a DNA based marker versus a genetic marker because that terminology is a little bit confusing. At first glance, we can think well, what, what is the difference? Well, genetic markers would be jeans with known location. So you know where these genes are on a chromosome and perhaps with say known alleles. So you've characterized different all variations of these genes and can look at well, what does this particular mutation mean in a population? How prominent is it? And you know which chromosome they're on and maybe even where they are on the chromosome. And this was determined in the past, mainly by linkage analysis and things like recombination studies. Of course, a big limitation of that is you can't do recombination studies in, for instance, human beings. So when we developed so much sequencing technology that led to the development of DNA based markers. So DNA based markers, markers are DNA sequences of known location, obviously also known sequence. We know what the base sequence is of that DNA bit and we know exactly where they are. And it's important to note that this can include noncoding as well as coding sequences. So in genetic markers, we're only going to be looking at coding regions of DNA. But in DNA based markers, we could be looking at non coding regions and particularly useful in terms of noncoding are things like short tandem repeats and single nucleotide polymorphisms, which often are mainly in the non coding regions of DNA. And those things vary even from individual to individual in a population. Uh they can be used for things like finger printing. So as we've sort of compared these two things, let's look through our answer choices, remembering that we're looking for the incorrect statement about an advantage of DNA based markers. So Cho says they are highly heritable. Well, that is true. They are inherited from parents. And in fact, uh various DNA based markers are even used in ancestry type studies, looking at descent um fraternity, things like that. So they are highly heritable. So that's not our correct answer choice. B says they are easy to assay. This is true. Also just by the very fact that we know their location and their sequence, you can have labeled primers that show you whether they're present somewhere you can sequence and see the, see, you can have a primer near where they are and look at the specific sequence and see exactly what the sequence is. So it's easy to assay and look for these. So that's not our answer choice. Then we're on to choice c environment dependent expression. Well, this will not be an advantage of DNA based markers because they can include non coding regions as well. The DNA sequence is the DNA sequence inherited from the parents. It is not dependent on the environment as opposed to genes where whether or not they're expressed can be affected by the environment can be affected by epigenetic modifications. So choice C is going to be in our, our answer of something that is not an advantage of DNA based markers. Finally, we're onto choice D, they are pheno typically neutral. And this is also true. Again, when you have things that vary from individual to individual, you wouldn't want it to have huge phenotypic effects. Uh because that would have consequences if this variation in a short tandem repeat or these little single nucleotide polymorphisms caused huge issues or huge differences in phenotypic expression. So in general, these DNA based markers are pheno typically neutral. So that is an advantage of these type of markers. So not our answer choice. So again, which of the following advantages of DNA markers is incorrect choice. C environment dependent expression. See you in the next video

Watch next