Explain why changes in the regulation of developmental genes may have played such a large role in the evolution of new forms.

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Accepted Answer

Hi everyone. Let's look at the next question. What makes scientists suspect that large scale evolutionary transformations are caused by the changes in the expression of developmental genes? Let's think about what is meant by large scale evolutionary transformations. These are these really dramatic changes that you see sometimes in evolutionary history. Things like um hoofed animals becoming aquatic mammals over the course of evolution. So very very drastic changes in the morphology of those species. Um Or hard shelled insects evolving wings. So these things that you see are suddenly like almost leaps in evolution. Big giant changes rather than small gradual ones. And it's saying that scientists suspect that these large scale transformations are caused by changes in the expression of developmental genes. So those genes are the very very beginning of development uh doing things like the orientation dorsal versus ventral segmentation genes, things like that. So let's look through our answer choices and see what makes sense here. And it says, Choice A says because of the change in the DNA sequence. If the expression has changed. Well this is not a true statement. If the expression has changed, this does not change the D. N. A sequence expression has to do with promoters inhibitors, things like that. Um Just when a certain gene is transcribed, it doesn't change the sequence itself. That would be a mutation. So Choice A is not our correct answer, choice B says because a change in these genes can significantly affect the morphology and this is our correct answer here. Those genes those developmental genes operating very early in development do have such a such a strong effect because you're operating the level of just a small number of cells and you're setting up the basic structure of the organism. That if you have a change in any of these genes, you have drastic effects on the morphology. Things like a leg growing where an eye should be. So that makes sense. That changes in expression of these genes which we know considerably affect morphology would be behind large scale evolutionary transformations. Um Because you have again a significant effect on morphology, a large scale evolutionary transformation. So in both cases big changes caused by changes to these genes. Choice, he says. Because any mutation to these genes can make the organism non viable. This is not a true statement. Um The organism is not necessarily non viable if there's a mutation in the genes, sometimes it is but not always. So that's not a true statement. And finally, choice D because an alteration of these genes creates a post psychotic barrier. Let's recall what a post psychotic barrier is. It's when you have reproduction or development blocked. After fertilization and zygote development, that's the name. Post psychotic. Um So pre psychotic pre barrier would be if say fertilization was blocked. Um But in this case you either have low viability of the embryo. So the zygote fertilization occurs. The zygote forms but the embryo doesn't develop any further. Um Hi you know low viability at different stages of development or offspring infertility. So the zygote develops. Embryo develops offspring born but is infertile. And this is not necessarily a not necessarily result of alteration of these genes. Um You most often see this in the case of hybrid meeting um as a result of perhaps different numbers of chromosomes that don't pair up correctly. So this is not our correct answer. So again, we're saying what makes scientists suspect that large scale evolutionary transformations are caused by the changes in the expression of developmental genes. Choice B. Because a change in these genes can significantly affect the morphology. See you in the next video.

Explain why changes in the regulation of developmental genes may have played such a large role in the evolution of new forms.

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Key Concepts

Developmental Genes

Gene Regulation

Evolutionary Developmental Biology (Evo-Devo)