ch16: control of gene expression

Question 1

gene expression

Answer 1

conversion of genotype to phenotype

Question 2

gene expression is most commonly controlled at

Answer 2

transcription initiation

Question 3

regulatory proteins bind to

Answer 3

DNA (block or stimulate transcription)

Question 4

both prokaryotes and eukaryotes regulate gene expression in response to their

Answer 4

environment

Question 5

prokaryotes (3)

Answer 5

• single celled
• need to divide as rapidly as possible
• need to survive rapid changes in availability of nutrient/resources

Question 6

eukaryotes (2)

Answer 6

• multicellular
• need to maintain consistancy (homeostasis)

Question 7

gene expression is often controlled by

Answer 7

regulatory proteins binding to specific DNA sequences

Question 8

the DNA is double-stranded. how do the regulatory proteins recognize the specific DNA sequences

Answer 8

by binding to the major grooves , each of the four bases extend a unique set of chemical groups into the major grooves of the DNA double helix

Question 9

common feature of DNA binding domains (2)

Answer 9

• protein a helix or B sheet that can read the DNA sequence through the groove of the DNA
• often found in pairs or more to make sure transcription occurs in correct direction

Question 10

positive control

Answer 10

increases frequency of transcription initiation

Question 11

activators

Answer 11

enhance binding of RNA polymerase to the promoter

Question 12

negative control

Answer 12

decreases frequency of transcription initiation

Question 13

repressors

Answer 13

block RNA polymerase from initiating transcription; bind to operators

Question 14

operators

Answer 14

sites on DNA

Question 15

effectors

Answer 15

molecules that help activators or repressors do their jobs

Question 16

inducer

Answer 16

bind repressor and blocks its ability to bind operator so that transcription can occur

Question 17

corepressor

Answer 17

bind repressor so it can better bind operator and block transcription

Question 18

inducible genes (3)

Answer 18

• regulated by induction
• genes for catabolic pathway enzymes
• enzymes are produced in response to presence of a substrate
  ex. digestion of lactose

Question 19

repressible genes (4)

Answer 19

• regulated by repression
• genes for anabolic pathway enzymes
• building up molecules
• enzyme production is blocked in response to presence of the product
  ex. synthesis of tryptophan: block production of enzymes to make tryptophan when enough of it is already present

Question 20

genes for enzymes involved in the same metabolic pathway in prokaryotes are often organized in

Answer 20

operons (groupings of multiple genes, all transcribed at the same time)

Question 21

CAP binding site

Answer 21

increases polymerase efficiency

Question 22

in the absence of lactose, LAC repressor is

Answer 22

expressed, binds to the operator, and blocks transcription

Question 23

when bacteria is placed in a dish with glucose and lactose, which one will it eat first

Answer 23

glucose

Question 24

eukaryotic regulation is more complex than prokaryotic regulations because

Answer 24

• eukaryotes have DNA organized into chromatin which complicates protein-DNA interaction
• eukaryotic transcription occurs in nucleus
• much more DNA involved in regulating eukaryotic genes

Question 25

promotor is always —— of the operator

Answer 25

upstream

Question 26

general transcription factors (4)

Answer 26

• bind to TATA box in the core promotor region
• necessary for the assembly of a transcription apparatus and recruitment of RNA polymerase II to a promotor
• for an initiation complex
• required for transcription

Question 27

specific transcription factors (3)

Answer 27

• bind to their unique sequences upstream of core promotor
• called activators: bind to enhancers (sites upstream of core promoter)
• increase the level of transcription in certain cell types or in response to signals

Question 28

core promotor forms the binding site for

Answer 28

general transcription factors

Question 29

enhancers are the binding site of the

Answer 29

specific transcription factors

Question 30

coactivator

Answer 30

enhance transcription

Question 31

corepressors

Answer 31

inhibit transcription

Question 32

DNA wound around histone proteins to form

Answer 32

nucleosomes

Question 33

nucleosomes may block

Answer 33

access to promotor

Question 34

histones can be modified to result in

Answer 34

greater condensation

Question 35

methylation

Answer 35

adding a CH3 onto a histone tail; block accidental transcription of genes that are already turned off

Question 36

acetylation

Answer 36

adding an Oc2H3 onto a histone tail; interferes with tails bonding with DNA and allows access for transcription

Question 37

alternative splicing

Answer 37

introns are spliced out of pre-mRNAs to produce the mature mRNA

Question 38

miRNA

Answer 38

encoded separately into the genomes and repress specific genes

Question 39

siRNA

Answer 39

halt the production of proteins by interfering with RNA production

Question 40

lysosome

Answer 40

contains proteases for nonspecific protein digestion

Question 41

proteasome

Answer 41

digests proteins that are specifically marked for destruction; tagged with the protein ubiquitin