The following predictions ask you to consider how genetic regulat...

Question

The following predictions ask you to consider how genetic regulatory cascades provide positional information. Select True or False for each statement.
T/F Mutation of a gene at one level of a regulatory cascade will affect the expression of genes at all levels of the cascade.
T/F Mutation of a gene that is expressed later in a regulatory cascade will affect a smaller region of the body than mutation of gene that is expressed early in the cascade.
T/F In the regulatory cascade used by Drosophila, a gene at one level of the cascade will be controlled only by genes at the level immediately above it.
T/F Genes that control the largest regions of the Drosophila embryo are not transcribed in the embryo.

Accepted Answer

Hi everyone here's our next problem. Hawks genes such as those in flies are controlled by a cascade of regulatory genes during the developmental stage. The structure is refined into broad sections, smaller sections and actual body segments. What will happen if the regulatory gene expressed at the initial stage of the cascade mutates or is disrupted? So the hawks genes are responsible for the development of the basic anatomical structures, particularly their organization. So as it says, first into broad sections, so you know, branded back, anterior uh dorsal, ventral, anterior, posterior and then into sections and segments. Uh So they develop where those structures appear on the body. So if the regulatory genes at the very beginning of this whole cascade are mutated or disrupted, you're going to have segments that do not develop in the right place. You might have legs develop in the front where the eyes are supposed to be. So, Choice A Indeed says segments will not develop in their right positions. So that would be the answer here. Let's just be thorough and look through the other choices. Choice B says development of internal organs will be delayed. Well that's not a correct answer. We're going to be looking at actual segments being in the wrong place. Choice C says there will be a loss of function among the body parts. Well that's not a correct answer. You could have functional legs or wings and that the structure is correct but it's in the wrong location and choice D says other genes will be deleted from the sequence? That's not correct. You're not deleting any genes. Um They're just being, you know, perhaps they're mutated so they're not functional um or there's a problem with their expression but they won't actually be deleted from the genome. So I hope that video helps again. Our answer is that if a mutation or disruption happens at the initial stage of the cascade controlled by the hawks genes, choice a segments will not develop in their right positions. See you in the next video.

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