Biochemistry 2280A Lecture Notes - Lecture 23: Consensus Sequence, Operon, Prokaryote

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17 Dec 2015

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Transcription is the first step in the expression of any gene, and is. For many genes, transcription is the most regulated step the most frequently regulated step in gene expression (fundamentally important step in gene expression) Promoter: the dna sequence required to initiate transcription of a. Terminator: the dna sequence require to stop transcription. Operon: a set of genes transcribed from a single promoter and thus expressed from a common rna. Green is promoter sequence to initiate transcription. Produces an rna from a position called +1 (where the rna starts, Terminated at a sequence called the terminator. Between that, can have a group of protein encoding genes. 3 independent protein products, made from the same rna. Space downstream is +2, upstream is -1 (no 0"s) 10 and -35 sequence elements are found in bacterial promoters. Don"t need to remember what the sequences are. Upstream from the +1 site remember that they are specific sequences (6 bases in length)

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1 DNA sequences found in introns provide [A] amino acid sequence information.

[B] regulatory information.
[C] no known useful information.

[D] structure for the gene.
[E] alternative DNA splicing possibilities.

3. The TATA box is a(n)
[A] sequence close to the promoter region of many genes.
[B] square-shaped sequence.
[C] enhancer consensus sequence.
[D] activator sequence necessary for proper translation.
[E] None of the above

5. Regarding genes and gene expression, which of the following is not a difference between prokaryotes and eukaryotes
[A] Eukaryotic DNA does not contain a TATA box close to the initiation site as does prokaryotic DNA.

[B] In eukaryotes, RNA polymerase requires

'transcription factors'or initiation.

[C] Prokaryotic genes are often grouped together in

operons.

[D] In eukaryotes, the regulation of several genes at once requires common control elements in each of the genes.
[E] There is a diversity of eukaryotic polymerases that is reflected in the diversity of eukaryotic promoters.

10) In eukaryotic cells, a repressor

[A] is made of DNA.
[B] binds to the enhancer region to block transcription. [

C] is located both upstream and downstream from the promoter.
[D] binds to the operator to block RNA polymerase.

[E] binds to a silencer to reduce transcription rates.

Coordinated regulation of genes in eukaryotic cells [A] is the result of positioning the same regulatory sequence in front of each gene.
[B] results from all of those genes being under the control of one promoter.

[C] occurs because related genes all have the same

operons.
[D] occurs because enhancers cause DNA to bend.

1. What is the term when the product of a biochemical pathway inhibits the activity of the first enzyme of a pathway?

		feedback inhibition.
		activator inhibition.
		diffusional regulation.
		enzyme activation.

2. Through control of gene expression, prokaryotes respond to changing __________ conditions.

		internal
		protein
		environmental
		genetic

3. A protein that negatively regulates transcription by binding to the operator is known as the

		operon
		repressor
		activator
		inducer

4. During attenutation, when tryptophan levels are high, the ________ stem-loop forms and transcription ________ the trpL gene.

		1-2, ends just past
		3-4, ends just past
		1-2, continues beyond
		3-4, continues beyond

5. The process of turning on the expression of a gene in response to a substance in the environment is called:

		constituation.
		repression.
		induction.
		catabolism.

6. What is a function of some specific transcription factors?

		to bind to the promoter region of the gene to facilitate the proper alignment of the RNA polymerase
		to bind to the centromere to induce meiosis
		to bind to enhancer regions to help regulate gene transcription
		to bind to the operator to recruit sigma factor

7. How does exposing an E.coli cell to glucose affect the regulation of the lac operon via CAP?

		cAMP binds to CAP and transcription is increased.
		cAMP binds to CAP and transcription is decreased.
		cAMP does not bind to CAP and transcription is increased.
		cAMP does not bind to CAP and transcription is decreased.

8. The lac repressor protein works when mutations in the repressor gene and structural genes are:

		in cis or in trans.
		in trans only.
		in cis only.
		in both prokaryotes and eukaryotes.

scarletwombat949

Please provide brief (one sentence) answers:

a) The Mycoplasma chromosome codes for 500 genes, yet it has about 20 promoters. Provide a brief explanation for how this is possible.

b) How many seconds would it take the bacterial RNA polymerase to synthesize an mRNA of 5,000 bases?

c) How many mistakes would the bacterial RNA polymerase make while synthesizing an mRNA of 30,000 bases?

d) Sigma (?) protein by itself does not bind to promoter sites. Predict the effect on transcription of a mutation enabling ? to bind tightly to the â35 region in the absence of other subunits of RNA polymerase.

e) What is the structure of the most common transcription terminator signal in E. coli, and what are 2 conserved features of the RNA sequence of this structure?

f) Why is RNA synthesis not as carefully monitored for errors, as is DNA synthesis?

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Biochemistry 2280A Lecture Notes - Lecture 23: Consensus Sequence, Operon, Prokaryote

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