WEEK 14-HW-Ch 18-2 - Homework for this Bio 181 class. Section 4. PDF

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Homework for this Bio 181 class. Section 4....

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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. __C___Feedback inhibition

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.

__L___Promoter ___B__Transcription __E___Operator __F___Operon ___A__Repressor __G__Corepressor __H___Inducer __K___Regulatory Gene __I___Repressible operon __J___Inducible operon __D___CAP

A. Binds to the operator to prevent transcription. 2. Label the following regions of the operon shown. Promoter, RNA polymerase, operator, genes, mRNA, polypeptides, regulatory gene, and repressor.

Op mRNA Repressor

Polypeptides Genes

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. Picture 1 is an inducible operon while the picture 2 is a repressible operon. 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. Picture 2 is an inducible operon while picture 1 is a repressible operon.

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? Amount of top is low when tryptophan concentrations are low. Results in inefficient translation of tandem trp codons.

8. In a prokaryotic cell, what happens to the trp operon, when tryptophan concentrations are high? Trp operon is repressed when tryptophan levels are high by binding the repressor protein to the operator sequence.

9. In a prokaryotic cell, what happens to the lac operon, when lactose concentrations are low? The lac operon only works when there is a greater presence of lactose.

10. In a prokaryotic cell, what happens to the lac operon, when lactose concentrations are high?

When the lactose concentration is higher, the lac operon is turned on.

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.

Unpacking of DNA. The location of a gene’s promoter, relative to both placement of nucleosomes and the sites where the DNA attaches to the chromo-some scaffold, can affect whether the gene is transcribed. In addition, genes within heterochromatin, which is highly condensed, are usually not expressed. Lastly, certain chemical modifications to chromatin—both to the histone proteins of the nucleosomes around which DNA is wrapped and to the nucleotides that make up that DNA—can influence chromatin structure and gene expression. Here we examine the effects of these modifications, which are catalyzed by specific enzymes.

First step in gene expression. Involves the copying of gene’s DNA sequence to make an RNA molecule. Performed by enzymes called RNA Polymerase, which link nucleotides to form an RNA strand.

The formation of mature and fully functional RNA species from primary RNA transcripts.

A reliable mechanism that has the ability to turn genes on or off. RNA is decoded to produce the amino acid sequence of a polypeptide by translation.

Degradation: Turns gene expression on/off (regulates) Protein Processing: Folding, cleaving, adding sugar groups, targeting for transportation

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...