Question

Explain the meaning of 'identity by descent' in the context of identifying genealogical relationship between individuals. In these analyses, why are segments of chromosomes (haplotypes) rather than individual STRs used to identify genetic relationships?

Accepted Answer

Hi, everyone. Let's look at the next problem. It says which of the following terms refers to the sharing of a segment of DNA between two or more individuals that is inherited from a common ancestor without any intervening recombination events. Choice A descent with modification B identity by descent C phylogeny or D modern synthesis. Well, when we look at shared segments of DNA that haven't had any recombination and those shared segments come from a common ancestor. This is referred to as choice B identity by descent. This is part of a genealogical analysis and obviously the greater the number of these shared segments, the greater the degree of relatedness between those individuals. And that's how when doing genealogical analysis, you estimate what type of relationship the two individuals have. Let's look quickly at our other answer choices. So we see why they're not correct choice C or excuse me. Choice a descent with modification just refers to the fact that species change over time that you have the, the accumulation of differences with each generation, you accumulate changes and that can lead to the development of new species. And this is just that basis of evolutionary theory. But not what we're looking to describe. So not our answer. Choice, choice C phylogeny. The study of how species descend from common ancestors, how they're related to each other, but not what we're looking for here. So let's cross that off and then finally, choice d modern synthesis. This is the emerging of the theories and ideas of Mendel and Darwin. So Mendel showed us how genes were passed on to offspring. And Darwin, of course, theorized about mutations arising and then being selected for or against and that leading to species change and speciation. So Mendel sort of provided the mechanics of how those changes are passed on to offspring with Darwin showing how environmental pressures act to select for or against different mutations. But the modern synthesis refers to taking those two theories and ideas and merging them together. But that's not what we're looking for here. So it's not our answer choice. So again, the sharing of a segment of DNA that's inherited from a common ancestor and hasn't been changed by intervening recombination events. This choice B identity by descent. See you in the next video.

Explain the meaning of 'identity by descent' in the context of identifying genealogical relationship between individuals. In these analyses, why are segments of chromosomes (haplotypes) rather than individual STRs used to identify genetic relationships?

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