Question

Eukaryote gene regulation question... about the yeast... please help me...

3. (7 points total) You are studying a set of genes in yeast (a eukaryote) that are required for the utilization of mannose. Mannose is a sugar that can be used by yeast cells but they will preferentially use glucose if it is available; this is similar to how the galactose genes work. Since you are a geneticist you study the genes by mutating them so they won't work and observing the effect. There are several genes (man -1 man-4, man-8 and man-10) that when mutated fail to utilize mannose. A mutation in any one of these genes affects only the gene itself; all of the others are normal.I a) Are man -1, 4, 8 and 10 structural or regulatory genes? How do you know (1 point)T b) There is another gene, which is called man-3. When it is mutated, none of the others listed in part A are expressed. What do you think man-3 probably does and why? (2 points) c) There are two additional genes, called man-7 and man-2. When man-7 is made mutant, the genes in part a are all expressed whether or not mannose is present. When man-2 is mutated, all the genes remain inactive, even when there is lots of mannose present. Briefly suggest functions for these two genes. (2 points)T d. Suppose you had a temperature-sensitive mutation of man-7 that functioned at temperatures below 27C but not above 35C. Suppose you grew your man-ts yeast cells with no glucose and plenty of mannose. One plate is incubated at the permissive temperature and one at the restrictive temperature. Explain what will happen to the cells on each plate and why (2 points).

Answer 1

Answer (a): man-1,4,8 and 10 are structural genes because they are not regulation the whole operon. Inspite of this they are being operating by some other genes.

Answer (b): man-3 is a regulatory gene because its mutation is controlling the expression of all the structural genes.

Answer (c): man-7 is repressor gene hence, if it is getting mutated it does not have any affect on the gene expressor because mainly it plays a role in inhibiting the gene expression by blocking the site of RNA polymerase. So, if it is getting mutated then its effect will be reduce and RNA polymerase can easily bind at the premoter region and can proceed the transcription which followed by tranlation that results into the structural gene expression.

man-2 is inducer gene. the role of inducer gene is to bind with repressor and inactivate it. if this gene will get mutated then the inducer will not able to bind with the repressor hence, repressor will be in active state and bind to the premoter region and inactivate the further gene expression of all the structural genes.

Answer (d): Plate which was grown at the permissive temperature with mutated man-7 gene will show thegrowth of the cells but not that much. cells will show less growth. But the plate incubated at restrictive temperature will not show any growth. because both the conditions are stress condition for the cells to grow in this case.