Biochemistry 2280A Chapter Notes - Chapter 8: Lac Operon, Lac Repressor, Regulatory Sequence

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greenporpoise254

23 Dec 2016

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Gene expression: genes selectively direct the synthesis of many proteins and. For most genes, the control of transcription is key. Only transcriptional control can ensure that no unnecessary intermediates are synthesized. All genes, both eukaryotes and prokaryotes, have regulatory dna sequences that are used to switch the genes on or off. These genes are reorganized by proteins called transcription regulators: transcriptional regulators bind to regulatory dna sequence that acts as the switch to control transcription. The surface of these proteins fit tightly against the surface of the dna double helix in that region. Proteins, usually dimers, insert into the major groove of the dna helix and make a series of intimate molecular contacts with the nucleotide pairs within the groove. Operons: the cluster in which genes are arranged in a chromosome transcribed on a single promoter. Operator: the short sequence in the operons promoter that binds regulatory proteins. External signals affect the gene expression of a cell such as hormones.

Related Questions

1. What reaction is catalyzed by reverse transcriptase and used in the laboratory to generate cDNA?

a. transcription of RNA to DNA

b. transcription of DNA to RNA

c. conversion of ribonucleotides into deoxyribonucleotides

d. translation of RNA to DNA

e. conversion of a ribonucleotide to a DNA double helix

2. In eukaryotic cells, _________determine the amount of mRNA arising from a particular gene.

a. transcriptional-level controls

b. RNA processing-level controls

c. translational-level controls

d. replication-level controls

e. b and c

3. In eukaryotic cells, _________determine how a primary transcript is converted to mature mRNA

a. transcriptional-level controls

b. RNA processing-level controls

c. translational-level controls

d. replication-level controls

e. a and d

4. In eukaryotic cells, _________determine when a particular mRNA is actually used in protein synthesis.

a. transcriptional-level controls

b. RNA processing-level controls

c. translational-level controls

d. replication-level controls

e. None of the above because protein synthesis takes place immediately

5. Under what circumstances do cells selectively activate and suppress their genes?

a. at different stages of embryonic development

b. in different tissues

c. exposure to different types of stimuli

d. No such circumstances exist in natureâcells express all their genes throughout life.

e. a, b and c

6. Which statement about the control of gene expression is FALSE?

a. A single gene may be controlled by different transcription factors.

b. A single transcription factor may be necessary for the expression of different genes.

c. Each cell type has a characteristic pattern of gene transcription, which is determined by the particular complement of transcription factors contained in that cell.

d. Expression of protein genes is primarily controlled in nucleoli

e. Control of gene transcription is complex and influenced by various circumstances.

7. What is thought to maintain X chromosome inactivation in females?

a. DNA acetylation

b. DNA methylation

c. RNA inactivation

d. Histone methylation

e. None of the above because both X chromosomes are active in females and males.

crimsonplatypus494

2. In eukaryotic cells, _________determine the amount of mRNA arising from a particular gene.

a. transcriptional-level controls

b. RNA processing-level controls

c. translational-level controls

d. replication-level controls

e. b and c

3. In eukaryotic cells, _________determine how a primary transcript is converted to mature mRNA

a. transcriptional-level controls

b. RNA processing-level controls

c. translational-level controls

d. replication-level controls

e. a and d

4. In eukaryotic cells, _________determine when a particular mRNA is actually used in protein synthesis.

a. transcriptional-level controls

b. RNA processing-level controls

c. translational-level controls

d. replication-level controls

e. None of the above because protein synthesis takes place immediately

5. Under what circumstances do cells selectively activate and suppress their genes?

a. at different stages of embryonic development

b. in different tissues

c. exposure to different types of stimuli

d. No such circumstances exist in natureâcells express all their genes throughout life.

e. a, b and c

6. Which statement about the control of gene expression is FALSE?

a. A single gene may be controlled by different transcription factors.

b. A single transcription factor may be necessary for the expression of different genes.

c. Each cell type has a characteristic pattern of gene transcription, which is determined by the particular complement of transcription factors contained in that cell. d. Expression of protein genes is primarily controlled in nucleoli

e. Control of gene transcription is complex and influenced by various circumstances.

7. What is thought to maintain X chromosome inactivation in females?

a. DNA acetylation

b. DNA methylation

c. RNA inactivation

d. Histone methylation

e. None of the above because both X chromosomes are active in females and males.

periwinklehorse209

Hello can you help me with the following questions:

1. Which part of an udder was transferred to an empty oocyte to clone the sheep Dolly?

a. blastocyst (I think its this one)

b. meiotic spindle

c. intact udder cell

d. nucleus

2. What is the principle of nuclear equivalence?

a. Differentiated cells have lost DNA that codes for other cell types.

b. All nuclei are the same shape.

c. Only nuclei of germ cells contain DNA capable of producing an entire organism.

d. The genome of every somatic cell contains information capable of generating any other cell type in the body.

3. A gene contains 6 exons, numbered 1-6. Which of the following mRNA isoforms is not a possible transcriptional product of this gene?

a. 1-2-3-4-5-6

b. 2-5-3-4

c. 2-4-5-6

d. 5-6

4. Which of the following is a mechanism used to alter gene expression using mRNA transcripts?

a. Different stability (longevity) of mRNA transcripts

b. Inhibition of translation of certain mRNAs

c. Production of small RNA molecules (microRNAs) that block translation

d. All of the above

e. None of the above

5. You have recently started working in an embryology lab and have obtained a large number of unfertilized zebrafish oocytes. You decide to treat the oocytes with RNAse (a protein that will degrade RNAs, but leave DNA proteins intact) prior to fertilizing them. Will the resulting embryos develop into normal fish?

a. Yes, because RNAs from sperm cells can replace those lost from the egg.

b. Yes, because intact DNA is the only factor required for development to proceed.

c. No, because RNAse treatment will damage the structure of the oocyte.

d. No, because maternal mRNAs are required for the early stages of development.

Biochemistry 2280A Chapter Notes - Chapter 8: Lac Operon, Lac Repressor, Regulatory Sequence

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