Biochemistry 2288A Lecture Notes - Lecture 4: Catabolite Activator Protein, Lac Operon, Trp Operon

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29 Dec 2017

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1 min 12 seconds: catabolite activator protein: transcriptional activator protein, lac operator: dna element that binds the repressor, cap binding site: dna element that binds cap. Lac operon is subject to regulation by both lactose and glucose. The operator of the lac operon is different than the trp operon operator. Lac operon operator exists downstream of the -10 sequences (towards the positive) while the trp operator is right between -10 and -35. Cap binding site is upstream of -35 sequences. When there is no lactose around, the repressor proteins bind to the operator of the lac operon, turning it off. What is he saying about (cid:498)in detail the something operator is in here(cid:499) 2 min 23 seconds. Catabolite activator protein must be bind to the dna for gene expression; cap increase the affinity of the dna for polymerase, the promoter itself have weak affinity for polymerase, thus transcription do not occur without cap binding.

Related Questions

5.) Is the CAP/cAMP effect on the transcription of the lac operon an example of positive or negative regulation? Why?

6.) Explain what happens during catabolite repression of the lac operon when both Glucose and Lactose are in high amounts. What is the biological relevance of this control?

7.) Why are O^c mutations said to be âdominantâ over I^s mutants?

8.) The rate of transcription of the trp operon in E. coli is controlled by what two regulatory processes? These two processes can regulate the trp operon up to about _____-fold due the combined effects of these processes. By what mechanisms do these two regulatory processes modulate trp operon transcript levels?

9.) Explain how high levels of tryptophan in the environment in which an E. coli cell is growing results in premature termination of transcription of the trp operon.

QUESTION 1

In the bacterial lac repressor, which of these occurs: (select all that apply)

		(a)In the presence of glucose and the absence of lactose, the repressor is actively produced.
		(b)The lac operon can be hyper-induced in the presence of low glucose by the 'cAMP binding protein' (CAMP).
		(c)In the presence of lactose and the absence of glucose the lac operon is repressed.
		(d)Allolactose is a byproduct of Î²-galactosidase, indicating high lactose when it builds up.

1.5 points

QUESTION 2

In eukaryotes the enhancer elements can be quite a distance upstream or downstream from the promoter, and transcriptional regulation is helped by protein:protein interactions.

True

False

1.5 points

QUESTION 3

The prokaryotic promoter contains a TATA box that is at -10bp upstream from the transcriptional start site.

True

False

1.5 points

QUESTION 4

During the addition of the poly A tail which of these occurs:(select all that apply)

		(a)The transcript is synthesized beyond the poly A site (AAUAAA).
		(b)The mRNA contains a 5â cap.
		(c)The transcript is cleaved 35nt downstream from the poly A site.
		(d)An enzyme complex containing an exonuclease and polyadenylate polymerase cleaves nearby the AAUAA site.
		(e)100-300 Aâs are added to the 5â end.

orangelocust889

1.) What type of control best describes the lac operon when it is regulated by allolactose? Explain the features of this type of regulation using the lac operon as an example.

2.) What is positive gene regulation?

a) when an activator protein binds to the operator of a gene to turn expression off

b) when a repressor protein binds to the operator of a gene to turn expression off

c) when an activator protein binds to the operator of a gene to turn expression on

d) when a repressor protein binds to the operator of a gene to turn expression on

e) when a protein binds to DNA to change gene expression

3.) In the lactose operon of E. coli, what is the function of each of the following genes or sites: a) regulator, b) operator, c) promoter, d) structural gene Z and e) structural gene Y?

a) regulator gene

b) operator

c) promoter

d) structural gene Z

e) structural gene Y

4.) In a negative, repressible regulatory mechanism, transcription of the structural gene(s) occurs in

a) the presence of the co-repressor, but not in its absence.

b) the absence of the co-repressor, but not in its presence.

c) the presence of the inducer, but not in its absence.

d) the absence of the inducer but not in its presence.

e) the absence or presence of the co-repressor.

What are answers and can you explain them to me?

Biochemistry 2288A Lecture Notes - Lecture 4: Catabolite Activator Protein, Lac Operon, Trp Operon

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