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.
A new mutation, designated 9, fails to complement mutants 1, 3, 5, 7, and 8. Wild-type recombinants form between mutant 9 and mutations 3, 5, and 8; however, no wild-type recombinants form between mutant 9 and mutations 1 and 7. What kind of mutation is mutant 9? Explain your reasoning.

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.

Table showing complementation results of eight bacteriophage mutants in genetics experiments.

A new mutation, designated 9, fails to complement mutants 1, 3, 5, 7, and 8. Wild-type recombinants form between mutant 9 and mutations 3, 5, and 8; however, no wild-type recombinants form between mutant 9 and mutations 1 and 7. What kind of mutation is mutant 9? Explain your reasoning.

Accepted Answer

Welcome back, everyone. Here's our next question. It says a group of four mutant E coli bacteria, ABC and D was studied for their ability to produce a certain enzyme. The mutants are known to result from point mutations. A new mutant designated E fails to complement mutant B wild type recombinant form between mutant E and mutants AC and D. Which of the following statements is correct regarding E choice A E has a point mutation in the same gene as mutants AC and D. Choice B E has a point mutation in the same gene as mutant B. Choice ce has a point mutation in a gene different from mutants, ABC and D or Choice D. None of the above. So let's think through the relationship of these genes to each other. Recalling that we do have that choice. D, none of the above is an option. So we're first told that E fails to complement B well, when you have no complementation. So that's between E and B. It means that the two mutations are in the same gene, you have a heterozygous offspring in which they each have each A uh chromosome has one of these mutations and you still have mutant offspring. So the both genes are mutated and you have a homozygous recessive offspring, essentially, even though they are slightly different mutations from each other. So E and B must be mutations in the same gene. So that points us right away to choice. B E has a point mutation in the same gene as mutant B. We know that's correct. So we can eliminate choice D and since we don't have any answer, choices that involve more than one correct answer, if I'm in a test, I want to move quickly, I would choose uh choice B and move on. Not even look at A N C here. But in the interest of being through, let's take a look at them. Choice. A says E has a point mutation in the same gene as mutants, AC and D. So we need to look a little further at our problem information. Our information told us that wild type recombinant form between mutant E and AC and D. So if you do have a wild type recombinant, that means that you had complementation. So when you have heterozygous offspring in which they each have in which each chromosome has one of these mutations, if you end up with wild type offspring, that means that those mutations occurred in different genes, so that you didn't end up with a homozygous recessive offspring, essentially. So since there's complementation between the mutant E and mutants ac and D then we would say that E is on a different gene than any of those mutations. So when we look at choice A, that must be incorrect since it says that it's in the same gene as AC N D. And then finally, choice C says E has a point mutation in the gene different from mutants, ABC and D. Well, we know it's in a gene different from AC and D, but it's on the same gene as choice B. So that's why choice C is not our correct answer. So again, the statement that is correct regarding Mutton, E this choice B E has a point mutation and the same gene as mutant B. See you in the next video.

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Key Concepts

Complementation

Point Mutation

Wild-Type Recombinants