Explain how the following mutations would affect transcription...

Question

Explain how the following mutations would affect transcription of the yeast GAL1 gene in the presence of galactose.

A mutation within the GAL80 gene that blocks the ability of Gal80 protein to interact with Gal3p.

Accepted Answer

Hi everyone. Let's look at our next question. It says Gal 80 is a repressor Having two binding partners. Goal four and goal three. What happens to the gal gene expression process in the presence of galactose, the medium. So these gal regulatory genes are all affecting the expression of the genes, the structural genes that produce the enzymes that break down galactose. So just as with the lack opera on the cell doesn't want to waste its energy producing these genes unless there's galactose present to digest. So let's think about the mechanism of these different regulatory genes and how they interact. Just going to post a little diagram here. So on the left we see the situation where there is no galactose present and in that case gal 80 is acting as a repressor. As our question mentions, we have gal four which is in its inactive form bound to gal 82 gal 80 is preventing the gene expression process by causing gal four remain in an inactive form. And then we've got gal three floating around here. Um not bound to anything. The gal genes are not being expressed. So we'll put off there on the right, we have a situation where galactose is present. So here's our galactose there. The galactose binds to gal three that changes its affinity for gal 80. It's now bound to Galati in preference to Galati being bound to gal four. Without that gal 80. Repressing it gal four is now in its active form. The gal genes are now being expressed. So with that in mind, let's look through our answer choices. Looking for the correct description of what happens when galactose is present in the medium Choice a says Gal binds to gal for enhancing the gal gene expression. Well when gal 80 is bound to gal four, as we see on the left situation here, that occurs when there's no galactose present because when Galati is bound to gal for that prevents that gene expression. So that's not a correct answer. So we'll cross that out. Choice B says Gal 80 binds to gal for preventing the gal gene expression. Well that is what happens when Galaxies bound to gal four. But that occurs when there is no galactose present. We're looking for the scenario that happens when galactose is there. So Choice B is not our answer. Choice C says Gal 80 binds with gal three, enhancing the inhibition of golfer and preventing gal gene expression. Well this is not correct when gal 80 is bound to gal three, that removes the inhibition of gal four and allows gal gene expression to see is not correct. Now we're down to choice D. It says Gal 80 binds with gal three, reducing the gal for inhibition activating the gal gene expression. Well this is our correct answer. And that is the scenario that's happening when galactose is present in the media. See you in the next video

Explain how the following mutations would affect transcription of the yeast GAL1 gene in the presence of galactose.
A mutation within the GAL80 gene that blocks the ability of Gal80 protein to interact with Gal3p.

Key Concepts

GAL1 Gene Regulation in Yeast

Role of Gal80 and Gal3 Proteins

Effect of Mutations Disrupting Gal80-Gal3 Interaction

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