Genetics: From Genes to Genomes, 5th edition
5th Edition
ISBN: 9780073525310
Author: Leland H. Hartwell, Michael L. Goldberg, Janice A. Fischer, Leroy Hood, Charles F. Aquadro
Publisher: McGraw-Hill Education
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Chapter 16, Problem 7P
Yeast genes have cis-acting elements upstream of their promoters, similar to enhancers, called upstream activating sequences or UASs. Several target genes involved in galactose utilization are regulated by one type of UAS called UASG, which has four binding sites for an activator called GAL4. Two target genes regulated by UAS are GAL7 and GAL10. The GAL80 protein is an indirect repressor of GAL7 and GAL10 transcription: At UASG,
GAL80 binds to GAL4 protein and blocks GAL4’s activation domain. In the presence of galactose, GAL80 no longer binds GAL4.
In which gene(s) (GAL4 and/or GAL80) should you be able to isolate mutations that allow the constitutive expression of the target genes GAL7 and GAL10 in the absence of galactose. In each case, what characteristics of the protein would the mutation disrupt?
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Gal4 is a transcription factor that activates transcription of galactose metabolism genes in yeast. These genes are ‘turned on’ when yeast cells need to metabolize galactose. To identify promoter sequences necessary for regulation of transcription of GAL1, reporter gene fusions were made and introduced into yeast cells. Deletions of GAL1 promoter were cloned upstream of LacZ gene. β-Galactosidase activity was measured in presence of galactose.
Shown below is a representation of the results obtained.
In the diagrams below (not to scale!):
• Construct 1 contains ~ 130bp of the promoter, which is predicted to have all the predicted/putative proximal promoter elements (indicated by the solid boxes) needed to regulate transcription of GAL1.• The stippled box is the core promoter.• The arrow represents the transcriptional start site for the reporter gene Lac Z• Number of + signs represents level of transcription• Star represents a mutation in DNA sequence at that location (few nucleotides…
The yeast gene SER3, whose product has a role in serine biosynthesis, is repressed during growth in nutrient-rich medium, so little transcription takes place, and little SER3 enzyme is produced, under these conditions. In an investigation of the repression of the SER3 gene, a region of DNA upstream of SER3 was found to be heavily transcribed when SER3 is repressed ). Within this upstream region is a promoter that stimulates the transcription of an RNA molecule called SRG1 RNA (for SER3 regulatory gene 1). This RNA molecule has none of the sequences necessary for translation. Mutations in the promoter for SRG1 result in the disappearance of SRG1 RNA, and these mutations remove the repression of SER3. When RNA polymerase binds to the SRG1 promoter, the polymerase travels downstream, transcribing the SGR1 RNA, and passes through and transcribes the promoter for SER3. This activity leads to the repression of SER3. Propose a possible explanation for how the transcription of SGR1 might…
RNAP can access the lacz promoter irrespective of whether CAP-CAMP is binding the CAP O
True
O False
Chapter 16 Solutions
Genetics: From Genes to Genomes, 5th edition
Ch. 16 - For each of the terms in the left column, choose...Ch. 16 - Does each of the following types of gene...Ch. 16 - List five events other than transcription...Ch. 16 - Which eukaryotic RNA polymerase RNA pol I, pol II,...Ch. 16 - You have synthesized an enhancerless GFP reporter...Ch. 16 - Prob. 6PCh. 16 - Yeast genes have cis-acting elements upstream of...Ch. 16 - A single UASG regulates the expression of three...Ch. 16 - Prob. 9PCh. 16 - a. Assume that two transcription factors are...
Ch. 16 - a. You want to create a genetic construct that...Ch. 16 - In Problem 12, you identified a genomic region...Ch. 16 - Prob. 13PCh. 16 - Prob. 14PCh. 16 - Genes in both prokaryotes and eukaryotes are...Ch. 16 - Prob. 16PCh. 16 - Prader-Willi syndrome is caused by a mutation in...Ch. 16 - The human IGF-2R gene is autosomal and maternally...Ch. 16 - Follow the expression of a paternally imprinted...Ch. 16 - Reciprocal crosses were performed using two inbred...Ch. 16 - Interestingly, imprinting can be tissue-specific....Ch. 16 - Prob. 22PCh. 16 - a. How can a single eukaryotic gene give rise to...Ch. 16 - A hunchback gene, a gene necessary for proper...Ch. 16 - You know that the mRNA and protein produced by a...Ch. 16 - You are studying a transgenic mouse strain that...Ch. 16 - Prob. 27PCh. 16 - Scientists have exploited the siRNA pathway to...Ch. 16 - Researchers know that Fru-M controls male sexual...Ch. 16 - The Drosophila gene Sex lethal Sxl is deserving of...Ch. 16 - Prob. 31P
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- The diagram below shows a closeup of regulatory proteins binding to one of the UASG elements near the GAL7, GALI0, and GALI genes, which code for the protein products needed for yeast to use the sugar galactose. The red triangle symbolizes an "effector" molecule that binds to Gal80p. In this hypothesis (which has since been shown to be incorrect), what could be happening to Gal80p when it is bound to the effector molecule that causes it to change its position and uncover the Gal4p transcriptional activation domain. Hint: think about what effector molecules do upon binding to proteins such as the the Lac repressor protein or the CAP protein. Galactose absent, glucose absent Gal80p. _Activation domain Gal4p dimer -Binding domain UASG Galactose present, glucose absent Activation domain Gal80p- Binding domain UASG For the toolbar, press ALT+F10 (PC) or ALT+FN+F10 (Mac).arrow_forwardGal 4 is involved in the regulation of galactose metabolism. Describe how transcription would be affected in the presence of a mutation that resulted in an inability of Gal80 to enter the nucleus?arrow_forwardIf the lacl gene is mutated so that the repressor protein no longer binds to lactose, what will be the effect on the expression of B-galactosidase in lactose's presence and absence? Explain. If the promoter for lacl is mutated so that the expression of the repressor increases, what will be the effect on the expression of B-galactosidase in the presence and absence of lactose? Explain. D. (Extremely tricky question!) Describe the behavior of the lac operon assuming that the lacl gene has been mutated so that the repressor now binds to DNA in the presence of lactose but cannot bind to DNA in the absence of lactose.arrow_forward
- Which of the following is the most likely result of a mutation in the lac operator that prevents release of the depressor protein? Choose 1 answer: (A)The lactose permease protein will be produced, even in the absence of lactose. (B) Transcription of the structural genes will be blocked, even in the presence of lactose. (C) The catabolite activator protein will be bound to the CAP site, even in the presence of glucose. (D) Expression of the lacI gene will be repressed, even in the absence of glucose.arrow_forwardMost eukaryotic promoters have binding sites for several different transcription factors, and the frequency with which transcription is initiated at a promoter depends on the specific combination of transcriptional regulators bound to their binding sites in that promoter. Transcription of the slither gene in garter snakes is regulated by the transcriptional activators Python and Boa and the transcriptional repressor Sidewinder. Each of these proteins has one binding site in the slither promoter; the affinity of Boa for its binding site is 30 times higher than the affinity of Python for its binding site and 6 times higher than the affinity of Sidewinder for its binding site. Under conditions where Sidewinder is 10 times more abundant than Python, and Python is 3 times as abundant as Boa, would you expect transcription of the slither gene to be activated or repressed? Show or briefly explain how/why you predicted the outcome you chose.arrow_forwardIIVY is a LysR regulator, and it helps control transcription of a neighboring gene, ilvC. IlvY can either bend the DNA and block RNAP's access to ilvC's -35 promoter site, or it can allow access to the ilvC -35 site, thereby promoting ilvC transcription. What determines whether llvY is repressing or activating transcription from the ilvC promoter? The presence of the co-inducer acetolactate - acetolactate binds to llvY and changes llvY's shape such that it doesn't block the -35 of the ilvC promoter. IlvY represses ilvC transcription when the IlvC protein is bound to llvY, and it activates ilvC transcription when the lvC protein is not present to bind to llvY. The presence of the co-inducer valine - when valine is present, it binds llvY and causes llvY to repress transcription from the ilvC promoter. The presence of the co-inducer acetolactate - acetolactate induces negative supercoiling at the ilvC promoter, which represses ilvC transcription.arrow_forward
- Searching the yeast Saccharomyces cerevisiae genome, researchers found approximately 4,000 DNA sites with a sequence which could potentially bind the yeast transcription factor GAL4. GAL4 activates the transcription of galactose genes. Yet there are only 10 GAL4-binding sites which control the genes necessary for galactose metabolism. The GAL4 binding sequence is CGGAT#AGAAGC*GCCG, where # is T, C or G, and * is C or T. In one chromatin immunoprecipitation experiment (ChIP), yeast growing on galactose were lysed, and subjected to cross-linking reagents which cross-linked transcription factors and activators to DNA. Next the DNA was sheared into small fragments, and antibodies to GAL4 were added. These antibodies coprecipitated the GAL4 and the DNA it was cross-linked to. The cross-linking was then chemically reversed, and the DNA was isolated, cloned into a library of plasmids and sequenced. Results showed that only 10 different DNA sequences had GAL4 bound. Since the…arrow_forwardThe lac genotypes are as shown below: P+OcZ-Y+A+// P¯O+Z+Y+A+ (i) The lac operon consists of three structural genes, lacZ, lacY and lacA. Which structural genes are involved in lactose metabolism? Explain. (ii) Draw and explain how lactose repress the gene expression in lac IS/I- heterozygote. (iii) What is the function of the promoter in the bacterial operon?arrow_forwardExplain how the following mutations would affect transcription of the yeast GAL1 gene in the presence of galactose. (a) A deletion within the GAL4 gene that removes the region encoding amino acids 1 to 100. (b) A deletion of the entire GAL3 gene. (c) A mutation within the GAL80 gene that blocks the ability of Gal80 protein to interact with Gal3p. (d) A deletion of one of the four UASG elements upstream from the GAL1 gene. (e) A point mutation in the GAL1 core promoter that alters the sequence of the TATA box.arrow_forward
- Discuss in general terms the principle of the regulation of theexpression of the trp gene with attenuation in bacteria.arrow_forwardThe genes that encode the enzymes for arginine biosynthesis are located at several positions around the genome of E. coli, and they are regulated coordinately by a transcription regulator encoded by the ArgR gene. The activity of the Argr protein is modulated by arginine. upon binding arginine, Argr alters its conformation, dramatically changing its affinity for the DNA sequences in the promoters of the genes for the arginine biosynthetic enzymes. given that ArgR is a repressor protein, would you expect that ArgR would bind more tightly or less tightly to the DNA sequences when arginine is abundant? if ArgR functioned instead as an activator protein, would you expect the binding of arginine to increase or to decrease its affinity for its regulatory DNA sequences? explain your answers.arrow_forwardEnvZ/OmpR proteins are a part of a two component signal transduction/phosphorylation system that interacts with ompC and ompF genes. Relative to each promoter, where would you predict phosphorylated OmpR would bind the ompC and ompF genes?arrow_forward
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