WEEK 14-HW-Ch 18 - Work PDF

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Chapter 18

BIO 181: Chapter 18 In class Activity Prokaryotic Gene Regulation 1. Match the following vocabulary terms to their correct definition. A. Binds to the operator to prevent transcription. B. Process by which DNA is converted into RNA C. The product of a metabolic pathway inhibits its own production, when the product is in high concentration. D. In a lac operon, a protein that binds to DNA and stimulates transcription. E. Often found in the promoter, the switch that controls RNA polymerase access to the DNA. F. Stretch of DNA that consists of the promoter and the genes required for protein production. G. A small molecule that cooperates with the repressor protein to switch the operon off. H. In the lac operon this molecule inactivates the repressor. I. The type of operon that is “always” on but can be inhibited under certain conditions. J. The type of operon that is “always” off but can be stimulated under certain conditions. K. This gene produces the repressor. L. Region on the DNA that the RNA polymerase binds to.

C Feedback inhibition L Promoter B Transcription E Operator F Operon A Repressor G Corepressor H Inducer K Regulatory Gene I Repressible operon J Inducible operon D CRP

2. Label the following regions of the operon shown. Promoter, RNA polymerase, operator, genes, mRNA, polypeptides, regulatory gene, and repressor. Regulatory gene

RNA Polymerase Operator

Promoter

genes

trpE

trpD

trpC

trpB

trpA

mRNA

Repressor polypeptides

3. Determine if the 2 images shown are of a repressible operon or an inducible operon. Determine which image is an example of gene expression and which is of gene inactivation. Inducible operon, gene expression

4. Determine if the 2 images shown are of a repressible operon or an inducible operon. Determine which image is an example of gene expression and which is of gene inactivation. Repressible operon, gene inactivation

5. If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then A. the amino acid inactivates the repressor. B. the repressor is active in the absence of the amino acid. C. the amino acid acts as a corepressor. D. the amino acid turns on transcription of the operon. 6. What would occur if the repressor of an inducible operon were mutated so it could not bind the operator? A. irreversible binding of the repressor to the promoter B. reduced transcription of the operon’s genes C. buildup of a substrate for the pathway controlled by the operon D. continuous transcription of the operon’s genes

7. In a prokaryotic cell, what happens to the trp operon, when tryptophan concentrations are low? It gets turned “on”

8. In a prokaryotic cell, what happens to the trp operon, when tryptophan concentrations are high? It gets turned “off”

9. In a prokaryotic cell, what happens to the lac operon, when lactose concentrations are low? The lac repressor binds tightly to the operator and prevents transcription by RNA polymerase

10. In a prokaryotic cell, what happens to the lac operon, when lactose concentrations are high? The lac repressor loses its ability to bind DNA

BIO 181: Chapter 18 Gene Expression Regulation Fill in the tables shown on how gene expression can be controlled at each of the following stages.

>Genes are highly impacted chromatin are generally not transcribed. >Histone acetylation loosens chromatin structure, enhancing transcription. >DNA methylation generally reduces transcription

>Regulation of transcription initiation: >DNA control elements in enhancers bind specific transcription factors. >Bending of the DNA enables activators to contact proteins at the promoter, initiating transcription >Coordinate regulation

>Alternative RNA splicing

>Initiation of translation can be controlled via regulation of initiation factors >Each mRNA has a characteristic life span, determined in part by sequences in the 5’ and 3’ UTRs.

>Protein processing and degradation subject to regulation

1. Which of the following best describes euchromatin and gene expression? A. The DNA is tightly compact and transcription occurs easily. B. The DNA is loosely compact and transcription occurs easily. C. The DNA is loosely compact and transcription does not occur easily. D. The DNA is tightly compact and transcription does not occur easily. 2. Histone Acetylation results in which of the following? A. The DNA becomes more tightly compact and transcription will not occur. B. The DNA becomes loose and transcription will not occur. C. The DNA becomes more tightly compact and transcription will occur. D. The DNA becomes loose and transcription will occur. 3. Which statement best describes transcription factors? A. Transcription factors encourage transcription. B. Transcription factors inhibit transcription. C. Transcription factors encourage translation. D. Transcription factors inhibit translation. 4. All of the following are ways in which to control gene expression at the RNA level except. A. Splicing B. Alternative splicing C. siRNAs D. DNA methylation 5. The proteasome controls gene expression at which level. A. DNA B. RNA C. mRNA D. Protein 6. Muscle cells differ from nerve cells mainly because they A. express different genes. B. contain different genes. C. use different genetic codes.

D. have unique ribosomes. 7. Which of the following is an example of post-transcriptional control of gene expression? A. the addition of methyl groups to cytosine bases of DNA B. the binding of transcription factors to a promoter C. the removal of introns and alternative splicing of exons D. gene amplification contributing to cancer 6. What would occur if the repressor of an inducible operon were mutated so it could not bind the operator? A.

irreversible binding of the repressor to the promoter

B.

reduced transcription of the operon’s genes

C.

buildup of a substrate for the pathway controlled by the operon

D.

continuous transcription of the operon’s genes...