You are studying similarities and differences in how org...

Question

You are studying similarities and differences in how organisms respond to high salt concentrations and high temperatures. You begin your investigation by using microarrays to compare gene expression patterns of S. cerevisiae in normal growth conditions, in high salt concentrations, and at high temperatures. The results are shown here, with the values of red and green representing the extent of increase and decrease, respectively, of expression for genes a–s in the experimental conditions versus the control (normal growth) conditions. What is the first step you will take to analyze your data? <>

Accepted Answer

Hi, everyone. Welcome back. Let's look at our next question. Comparative genomics can determine the similarities and differences between two genomes of interest. Which of the following serves as the initial step in comparing these two genomes. Choice A, determining the DNA repeats. Choice B, identifying the conserved symphony choice C, tracing the DNA markers in the genome or choice D alignment of the two sequences. So when we imagine comparing two genomes from two different species, kind of the first step, we're always going to look at is how do the two DNA sequences line up with each other to look for regions of similarity where they are similar, where they have the same sequence where they differ. So choice D alignment of the two sequences is going to be our answer here. One thing that might give us a little doubt or a little confusion is choice B identifying the conserved symphony. A symphony conserved symphony would be conserved gene location on a chromosome. So you'd be saying which chromosome has the gene for hand development for humans versus say chimpanzees and looking because things like translocation can affect where genes are and cause them to be separated over the course of evolution. So that would be a step and an early step in comparing genomes of different organisms. But given our access to databases today, kind of the basic first step is aligning DNA sequences to look for similarities and differences. So that's why choice B although it would be something you would do in comparing two genomes would not be the first step we'd look at. Well, once we've aligned the two sequences, we're going to see differences, things like changing nucleotides deletion of nucleotides, or you might have repetitions, duplications of entire DNA sequences that would show up when you try and align the two sequences. So that would give it B choice A determining DNA repeats. Again, that would be part of the comparison, but not the first step. Because in order to determine where DNA has been repeated, you have to align the sequences and compare them in the first place. So you first have to align the sequences before you can determine if a repeat has taken place. And then finally, choice C tracing the DNA markers in the genomes. DNA markers are those things like SNP S S T R S individual variation in various parts of the genome. And that would be more a part of comparing the genomes of individuals are the same species looking for ancestry relatedness change over time because this is what you look at when the genes are the same, you're the same species. But you want to look at variation among individuals. So that's why choice C wouldn't be our answer here. So again, the initial step in comparing two genomes of interest would be choice d alignment of the two sequences. See you in the next video.

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