Week 6

Question 1

sigma factors

Answer 1

needed by bacterial RNA polymerase, helps bind at promoters and initiate transcription, can’t bind properly without it

Question 2

RNA polymerases

Answer 2

enzyme responsible for transcription, synthesizes in the 5’-3’ direction

Question 3

mRNA synthesis

Answer 3

codes for proteins, transcription begins downstream of the promoter but upstream of the coding region

Question 4

operons

Answer 4

organizes prokaryotic genes, there are several downstream controlled by a single promoter

Question 5

trp operon

Answer 5

transcription of the trp operon produces the enzymes necessary to synthesize tryptophan, default state of this promoter is on, when bound to DNA the trp repressor prevents RNA polymerase from binding to the promoter, so no transcription of the trp operon when tryptophan is present

Question 6

lac repressor

Answer 6

when lactose is absent, the lac repressor binds to DNA so transcription is off; when lactose is present the lac repressor doesn’t bind DNA so transcription can proceed

Question 7

cAMP

Answer 7

generated by e coli when glucose is LOW, binds to CAP which activates transcription of the lac operon; if glucose levels are HIGH and cAMP is LOW, CAP does not activate transcription

Question 8

double positive feedback

Answer 8

memory unit where both units are EITHER on or off

Question 9

double negative feedback

Answer 9

memory unit when one unit is off and the OTHER unit is on

Question 10

genetic code

Answer 10

triplet based, redundant and unambiguous, non-overlapping, and universal

Question 11

AUG

Answer 11

start codon

Question 12

reading frame

Answer 12

3 base pairs that encode for an amino acid

Question 13

open reading frame

Answer 13

DNA sequence between a start and stop codon