Use a highlighter to color any amino acid that varies among the species. (Color that amino acid in all sequences.) d. In the M sequence, circle the amino acid(s) that differ from the C, G, R sequences, and draw a square around those that differ from the H sequence.

Video transcript

Hello everyone. Our next question says based on the sequence alignment of the different species, what species is most closely related to humans and chimpanzees and I'm given a short sequence of amino acids from a protein common to human. Mouse, chimpanzee, frog and fish and we need to look at which is most closely related to the human and chimpanzee. So let's start by highlighting the human sequence and the chimpanzee sequence and first seeing how they are similar or different. And I can see that in this particular segment, as I look down at the human and chimpanzee sequences are actually identical. It's not surprising given how closely related we are to each other. So now to find out which species is most closely related, I want to look for which species has the fewest number of differences to those two identical sequences. So I'm going to go through and highlight anywhere an amino acid differs from the human and chimpanzee identical sequences. So in this first column here, I see all three species, mouse, frog, fish have different amino acids in that place. The next column, everyone is identical. And I'm just going to go through the whole chart here, column by column and just highlighting any different amino acids here and then it will be quite easy to spot which sequence has the fewest number of differences. So just double checking that I hit them all and when we look at our entire chart, um we can see quite clearly that the mouse sequence has only a single amino acid difference from human and chimpanzee, whereas frog and fish have several differences. So that gives us a quick route to our correct answer. Look down at our choices of sea mouse and that makes intuitive sense to us as a mouse as our fellow mammals as opposed to frog and fish. So we can definitely eliminate A and B. Fish and frog choice D. Is cow, which isn't even on our chart, so that obviously can be eliminated as well. So our correct answer here, see mouse as the most closely related. See you in the next video.