You are working with a strain of yeast that has a mutation in GAL3 that inhibits its binding to GAL80. Which of the following is expected to happen when the yeast are grown in the PRESENCE of galactose? GAL structural genes will NOT be transcribed because GAL4 will not be able to bind to any of the promoters for GAL genes. GAL structural genes will NOT be transcribed because GAL80 will block the DNA binding domain of GAL4. GAL structural genes will NOT be transcribed because GAL4 will not be able to bind to any of the UASs for GAL genes. None of these choices GAL structural genes will NOT be transcribed because GAL80 will block the activation domain of GAL4.
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Gal80 is a repressor that binds Gal4 and masks its activation domain. Gal3 is the galactose sensor that, when bound to galactose, interacts with Gal80 to relieve Gal80’s inhibition of Gal4. Show more…
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Yeast genes have $c$ is-acting elements upstream of their promoters, similar to enhancers, called upstream activating sequences or UASs. Several target genes in- volved in galactose utilization are regulated by one type of UAS called $U A S_{G}$ which has four binding sites for an activator called GAL4. Two target genes regulated by $U A S_{G}$ are $G A L 7$ and $G A L I O$. The GAL 80 protein is an indirect repressor of $G A L 7$ and $G A L I O$ transcription: At $U A S_{C}$ GAL80 binds to GAL4 protein and blocks GAL4's activation domain. In the presence of galactose, GAL 80 no longer binds GAL 4 In which gene(s) $(G A L 4 \text { and/or } G A L 80$ ) should you be able to isolate mutations that allow the constitutive expression of the target genes $G A L 7$ and $G A L I O$ in the absence of galactose? In each case, what characteristics of the protein would the mutation disrupt?
Which statement about Gal gene expression in yeast is right Select one: a. In the presence of galactose, and absence of glucose, the activation domain of Gal4 is exposed, the Gal1 and Gal10 genes are expressed. b. In the absence of galactose and glucose, the activation domain of Gal4 is exposed, the Gal1 and Gal10 genes are expressed c. In the presence of galactose, and absence of glucose, the activation domain of Gal4 is covered by Gal80, the Gal1 and Gal10 genes are expressed d. In the absence of galactose and absence of glucose, the activation domain of Gal4 is exposed, the Gal1 and Gal10 genes are not expressed
Sri K.
Predict whether the GAL genes (Gal1, Gal7 Gal10 and Gal2) will be produced in the following yeast strains under the conditions noted. Use + to indicate that the GAL enzymes are synthesized at greater than basal levels, and - to indicate that the enzymes are not synthesized. NOTE: Gal4ts= a recessive temperature-sensitive allele of Gal4 Galactose absent Galactose present (a) wild-type (b) Gal4+/Gal4- (c) Gal3-/Gal3- (d) Gal80-/Gal80- (e) Gal4ts/ Gal4ts (at the permissive temperature) (f) Gal4ts/ Gal4ts (at the restrictive temperature) (g) Gal4+/ Gal4ts (at the restrictive temperature)
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