Consider the phylogenetic trees below pertaining to thre...

Question

Consider the phylogenetic trees below pertaining to three related species (A, B, C) that share a common ancestor (last common ancestor, or LCA). The lineage leading to species A diverges before the divergence of species B and C.

For gene Z, gene duplications have occurred in all species. Define orthology and paralogy relationships for the different Z genes. <>

Accepted Answer

Hello, everyone and welcome to today's video. So the human alpha and beta globin genes are both involved in oxygen transport in the blood. However, they have different specificities and are located on the frame chromosomes. These genes are an example of, well, let's go over each of our answer choices so that we may solve the problem. Let's begin by answer choice. A which is Ortho genes. Remember that these genes are going to be arising from a common ancestor and they have similar or identical function. But when we say that two genes are orthos, we're going to be mentioning them or comparing them across species, not within the same organism or within the same species as the question is stating, so we're going to cancel it out because the question is only talking about the human alpha and beta gloving gene. Let's move on. We have answer choice B which is analogous genes. So this is very similar to the Ortho genes and these are going to have however, no common ancestor. But, but again, when we say that two genes are analogs, we're going to be comparing them across species. And the question is stating in humans only. So we're also going to cancel analogous genes out. And then we have C and para genes are going to be genes that arise from a process called gene duplication. And therefore, they're going to have very similar functions within the same organism. And that is the main difference, these paraly genes, we're going to be able to compare them within an organism or within a species such as humans. So therefore, these human alpha and beta globin genes because they have the same function and they're found within the same organism. We're going to say that there are.

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