Regulation of Gene Expression

Question 1

What is spatial restriction of gene expression?

Answer 1

Differences in regulation of gene expression in different organs, tissues, cell types, or cells.

Question 2

What is temporal restriction of gene expression?

Answer 2

Differences in regulation of gene expression during different points of development, differentiation, cell cycle or inducible expression.

Question 3

Through what molecules does regulation of gene expression occur?

Answer 3

Specific transcription factors

Question 4

What is an operon?

Answer 4

A series sequentially grouped genes that encode proteins whose functions are involved in similar biological pathways

Question 5

Which of the following are true of operons? All of the genes are controlled by the same cis-acting elements; all of the genes are expressed as polycistronic mRNA; All of the genes can be turned on or off at the same time

Answer 5

All are true

Question 6

What is the segment if DNA that regulates the expression of genes present in an operon?

Answer 6

Operators

Question 7

Do transcription factors bound to operators typicaly activate or repress gene expression?

Answer 7

Repress

Question 8

What is the lac operon?

Answer 8

Prokaryotic operon that contains lacZ, lacY, and lacA all of which encode proteins that metabolize lactose

Question 9

Under what cellular conditions is the lac operon mostly highly expressed?

Answer 9

When glucose is absent or very low and when lactose is available

Question 10

What elements are contained in the lac operon?

Answer 10

The lac promoter, operator, CAP binding site, and three genes

Question 11

What is encoded by the lacI gene?

Answer 11

The lac repressor

Question 12

What is CAP? What is its function with regards to the lac operon? What is it activated by?

Answer 12

Catabolite Activator Protein is activated by cAMP and binds to the CAP-binding site of the lac operon to activate it

Question 13

What is the activity of lac operon expression when glucose is the only available sugar?

Answer 13

None of the lac operon genes are transcribed

Question 14

What is the mechanism of catabolite repression with regards to the lac operon?

Answer 14

The presence of glucose inhibits the activity of adenylyl cyclase- which causes low levels of cAMP and low ability of CAP to bind and activate transcription

Question 15

What is the level of lac operon transcription when both lactose and glucose are present?

Answer 15

Transcription of the operon is present but low

Question 16

What is the Trp Operon?

Answer 16

A series of 5 prokaryotic genes important for the synthesis of Tryptophan

Question 17

What is the effect of the binding of Trp to the Trp operon repressor?

Answer 17

It enhances the binding of the repressor to the operator

Question 18

What is attenuation?

Answer 18

The attenuating or pausing of RNA Pol once transcription has been initiated

Question 19

What is the stringent response?

Answer 19

Gene expression regulation in response to amino acid starvation

Question 20

The formation of which molecule is catalyzed by RelA?

Answer 20

Guanosine 5’-disphosphate 3’-diphosphate (ppGpp)

Question 21

Operons expressing what kind of proteins are suceptible to negative feedback inhibition?

Answer 21

Ribosomal proteins

Question 22

What area of specific transcription factors allows the binding of additional proteins or to facilitate the recruitment of the transcriptional initiation complex to inititate transcription

Answer 22

Transcriptional activation domain

Question 23

What is combinatorial control?

Answer 23

A eukaryotic method of gene expression regulation by which a limited set of regulatory proteins exert specific effects on gene transcription via unique combinations and interactions

Question 24

Through wat mechanism does cortisol affect gene expression?

Answer 24

Cortisol binds to its intracellular receptor, which moves into the nucleus, dimerizes and binds to the glucocorticoid response element in DNA

Question 25

What cis-acting element is found at the 3’ end of the Transferrin gene? What trans-acting element binds to it?

Answer 25

Iron-responsive element; Iron-regulatory protein

Question 26

When iron levels are high, what is the activity of IRPs? What effect does this have on the transferrin mRNA?

Answer 26

Iron is bound to the IRP, which lose their affinity for IREs, expediting the degradation of the transferrin mRNA

Question 27

What kind of RNA mediates RNAi?

Answer 27

microRNA

Question 28

What is the level of methylation on transcriptionally active genes compared to inactive genes?

Answer 28

Active genes are usually less methylated

Question 29

What DNA base is usually methylated?

Answer 29

Cytosine

Question 30

In RNAi, high complementarity of the miRNA with the target mRNA will have what consequences for the mRNA? Lower complementarity?

Answer 30

Degradation of RNA; inhibition of translation