Unit 6 - topic 5

Question 1

gene expression

Answer 1

prokaryotes and eukaryotes must be able to regulate which genes are expressed at any given time

Question 2

genes can be turned

Answer 2

“on” or “off” based on environmental and internal cues

Question 3

on/off refers to

Answer 3

whether or not transcription will take place
allows for cell specialization

Question 4

operons

Answer 4

group of genes that can be turned on or off

Question 5

operons have

Answer 5

three parts

Question 6

promoter

Answer 6

where RNA polymerase can attach

Question 7

operator

Answer 7

on/off switch

Question 8

genes

Answer 8

code for related enzymes in pathway

Question 9

operons can be

Answer 9

repressible or inducible

Question 10

repressible (on/off)

Answer 10

transcription is usually ON, but can be repressed (stopped)

Question 11

inducible (off to on)

Answer 11

transcription is usually OFF, but can be induced (started)

Question 12

regulatory gene

Answer 12

• produces a repressor protein that binds to the operator to block RNA polymerase from transcribing the gene
• always expressed, but at low levels
• binding of a repressor to an operator is reversible

Question 13

allosteric activator

Answer 13

substrate binds to allosteric site and stabilizes the shape of the enzyme so that the active sites remain open

Question 14

allosteric inhibitor

Answer 14

substrate binds to allosteric site and stabilizes the enzyme shape so that the active sites are closed (inactive form)

Question 15

inhibitor/respressor

Answer 15

allosteric site

Question 16

substrate

Answer 16

active site