An attribute of growth behavior of eight bacteriophage mutants...

Question

An attribute of growth behavior of eight bacteriophage mutants (1 to 8) is investigated in experiments that establish coinfection by pairs of mutants. The experiments determine whether the mutants complement one another or fail to complement These eight mutants are known to result from point mutation. The results of the complementation tests are shown below.

Identify the mutants of each gene.

Gene-mapping information identifies mutations 2 and 3 as the flanking markers in this group of genes. Assuming these mutations are on opposite ends of the gene map, determine the order of mutations in the region of the chromosome.

Accepted Answer

Hi, everyone. Let's look at our next problem. Four fruit fly mutants, ABC and D were studied for their ability to produce a certain eye pigment. The mutants are known to result from point mutations. The following table shows the results of the complementation tests between the mutants and we have a table with across the top ABC and D and on the left side, ABC and D and it shows with positive and negative sides whether the result of the complementation test was a negative, the two genes failed to complement each other and so generated still a mutant offspring or with a positive sign that the genes did complement each other. And therefore the offspring in the cross that makes a complementation test reverted to wild type gene mapping information identifies mutations B and D as the flanking markers in this group of genes. Which of the following could be a possible order of mutations in the region of the chromosome. And we have choice A B D AC choice BBC D A JO C B A CD. More choice DB DC A. Well, we're going to start with the information that we know what the flaking markers are, our problem says that B and D are the flaking markers. So that means that we must have B as the first mutation, D as the last. So let's look at our answer choices. And when we do that, there's only one choice that has that arrangement. And that's choice. C B A CD. We can actually eliminate all of our other answer choices. They all begin with B but none of them end with D. So we already have our correct answer without going any further. But just to be thorough and understand how to look at these complementation tests, we're going to double check that this is the correct order. So our answer choice has A and C in the middle. So B A CD, does that make sense? Well, we'd want to look at the results of complementation tests between A and C. So we do that by looking at our table, we find a on the left hand side and look across column across our four columns to find column C. And we see that that has a negative in it. And that means that A and C fail to complement each other. And we can double check if we look at row C on the left side and go to column A as expected. We see that's a negative as well. So what does this mean if they fail to compliment each other? That means they are likely mutations in the same gene. So, close to each other. And that does confirm what we see in our answer choice that A N C are in the middle next to each other as opposed to anywhere else. So we have our answer choice here. And that is choice C B A CD is the order a possible order of mutations in this region of the chromosome. See you in the next video.

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