chapter 24: control of gene expression - prokaryotes

Question 1

differential gene expression

Answer 1

a biochemical process that determines which genes respond to which signals or triggers depending on the condition

Question 2

transcription factors

Answer 2

• recognize a specific sequence of bases in DNA based on shape and partial charge to make hydrogen bonds
• bind to DNA to regulate transcription

Question 3

negative control transcription factors

Answer 3

regulatory protein shuts down transcription

Question 4

positive control transcription factors

Answer 4

regulatory protein triggers transcription

Question 5

operon

Answer 5

a group of genes that are transcribed together and regulated by a shared promoter and operator

Question 6

inducer

Answer 6

small molecule that triggers transcription of a gene

Question 7

operator

Answer 7

sequence of DNA that a transcription factor binds to

Question 8

activator

Answer 8

transcription factor protein that promotes transcription

Question 9

repressor

Answer 9

transcription factor protein that decreases transcription

Question 10

how is lac operon regulated

Answer 10

by an inducible repressor
- when repressor transcription factor is transcribed and translated from the lacI gene, and lactose is not present, neither protein necessary for lactose digestion is expressed

Question 11

when lactose is present, the repressor is

Answer 11

deactivated

Question 12

how is glucose involved in lactose digestion

Answer 12

• glucose prevents expression of gene for B-galactosidase
• the presence of lactose without glucose stimulates expression of the B- galactosidase gene

Question 13

CAP (catabolite activator protein)

Answer 13

• activated when cAMP is present
• when there is ample glucose outside cell, no cAMP synthesis, CAP does not bind to DNA to activate lac operon expression

Question 14

lactose only imported when glucose levels are?

Answer 14

low

Question 15

glucose low outside cell ->

Answer 15

cAMP high inside cell

Question 16

lac operon summarized

Answer 16

• lactose absent = repressor activated; operon not expressed
• lactose and glucose present = repressor inactivated, activator not activated, operon expressed at low levels
• lactose present glucose absent = repressor inactivated, CAP activated, operon expressed at higher levels

Question 17

the TRP operon

Answer 17

• regulated by a repressible repressor

Question 18

regulon

Answer 18

• a set of separate genes and operons that contain the same regulatory sequences and are controlled by a single type of regulatory protein
• typically differentially expressed in response to a particular “challenge” such as rise in temp or change in nutrients