7.4 Gene Expression

Question 1

are all proteins required for gene expression?

Answer 1

no, and intricate systems ensure all cells express genes required; gene expression responds to cellular environment

Question 2

insulin

Answer 2

hormone produced by pancreas that lowered blood glucose levels by promoting more glucose

Question 3

housekeeping cells

Answer 3

some proteins needed all the time to regulate processes like metabolism, growth, and DNA replication and transcription

Question 4

lac operon

Answer 4

cluster of genes that contain DNA sequences to regulate metabolism of lactose
- consists of promoter, operator, coding regions for enzyme to metabolize lactose

Question 5

operator

Answer 5

region in operon that has regulatory factors bind to repressor protein

Question 6

repressor protein

Answer 6

binds to operator to repress gene transcription

Question 7

no lactose?

Answer 7

lac repressor is active and binds to operator

Question 8

lactose present?

Answer 8

some binds to repressor and is rendered inactive and cannot bind to operator blocking transcription

Question 9

as concentration of lactose decreases?

Answer 9

amount of inactivated repressor decreases

Question 10

inducer

Answer 10

signal molecule that triggers gene expression of operon

Question 11

trp operon

Answer 11

regulates production of tryptophan in a cell

Question 12

tryptophan

Answer 12

important amino acid used to build proteins

Question 13

when is trp activated and inactivated?

Answer 13

activated in presence of tryptophan, inactivated in absence

Question 14

when tryptophan is present?

Answer 14

cell can conserve energy by using available and and stopping transcription of gene that code for enzymes involved in biosynthesis of amino acid

Question 15

when tryptophan is absent?

Answer 15

repressor protein is inactive and doesn’t bind to operate; RNA polymerase binds to promoter and transcription of genes for biosynthesis can proceed

Question 16

corepressor

Answer 16

signal molecule that binds to regulatory protein to reduce expression of operon’s genes

Question 17

eukaryotic control mechanisms

Answer 17

transcriptional
post-transcriptional
translational
post-translational

Question 18

transcriptional

Answer 18

regulates which genes are being transcribes (DNA to RNA) or controls rate at which transcription occurs; activator and repressor proteins bind to promoter and enhance or decrease rate of transcription, methyl groups added to cytosine bases in promoter –> RNA polymerase cannot bind and transcribe

Question 19

post-transcriptional

Answer 19

controls availability of mRNA molecules to ribosomes; pre-mRNA molecules undergo changes in nucleus, resulting in final mRNA before translation; alternative splicing occurs; diff combos of introns are removed and exons are spliced together

Question 20

translational

Answer 20

controls how often and how rapidly mRNA transcripts will be translated into proteins; variation of length of poly(A) tail related to rate of translation

Question 21

post-translational

Answer 21

controls when proteins become fully functional, how long they are functional, and when they’re degraded; presence of hormones may lengthen or shorten length of time that a protein is functional