Consider the even-skipped regulatory sequences in Figure 18.9....

Question

Consider the even-skipped regulatory sequences in Figure 18.9.

Explain what you expect to see happen to even-skipped stripe 2 if it is expressed in a Krüppel mutant background. What about a hunchback mutant background? A giant mutant background? A bicoid mutant background?

Diagram showing even-skipped gene enhancers, repressors, activators, and gap gene expression patterns across embryo segments. Diagram showing regulatory protein binding on eve stripe 2 enhancer and resulting stripe expression in different mutant backgrounds.

Accepted Answer

Welcome back. Everybody. Here's the next problem in a blink mutant background, we would expect to see that the even skipped stripe two expression is shifted posteriorly or towards the tail end of the embryo. Our answer choices are a hunchback B B coid C giant or D cripple. Well, let's just go through each of these genes and think about the effect of them on that expression of the even skip gene and stripe two. So if we look at the hunchback gene, we can recall that hunchback represses, represses the expression of the even skipped gene in the posterior region. So, in normal conditions in the posterior region of the embryo, the expression of that even skipped gene is repressed by the hunchback gene by the hunchback protein. So if that hunchback gene has a mutation makes it nonfunctional, then we would see expression of even skip stripe two shifted posteriorly since it now can be expressed in that region, since you no longer have a functional hunchback repressing it. So that's going to lead us to choice a hunchback as our answer. Let's just quickly look at our other choices. So we can understand why they are not correct choice B by coid. Well, bio is required for the expression of the even skip gene. And so if you had a bi coid mutant, you'd have a loss of expression of that even skip stripe too. So that's why choice B isn't correct. And then to, to see giant, well, giant is a repressor. I've even skipped in that stripe two region. It helps define the boundaries of it. So as a result, you would have an expanded region of expression of the even skip stripe too. So that's why that's not our answer. And then finally, choice D cripple and in this case, cripple represses the expression of even skipped in the anterior region of the embryo. And so if you had a mutant in the cripple gene, you would have the expression shifted the opposite way that we're looking for. So she'd have expression shifted anteriorly. So that's why choice D is not correct. So again, we're looking for the mutation that would cause the even skipped stripe two expression to shift in a posterior direction. And that's choice. A hunchback. See you in the next video.

Consider the even-skipped regulatory sequences in Figure 18.9.
Explain what you expect to see happen to even-skipped stripe 2 if it is expressed in a Krüppel mutant background. What about a hunchback mutant background? A giant mutant background? A bicoid mutant background?

Key Concepts

Even-skipped (eve) Stripe 2 Regulation

Role of Maternal and Gap Genes in Pattern Formation

Effects of Mutations in Gap Genes on eve Stripe 2 Expression

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