Lecture 16 P2

Question 1

tryptophan operon

Answer 1

affected by presence of tryptophan in the environment

Question 2

when tryptophan is low…

Answer 2

inactive repressor does not bind to the operon, transcription that makes trp occurs

Question 3

when tryptophan is high…

Answer 3

once production is high enough, the amino acid trp will bind to the repressor making it active and allowing it to bind to the operator, halting transcription

Question 4

structure of trp operon

Answer 4

regulatory sites within the transcribed region, aka the 5’ UTR region. this is upstream from the coding sequence and includes a ribosome binding site on the left

Question 5

5’ UTR region

Answer 5

allows for formation of secondary structures in mRNA, known as attenuation
1&2 and 3&4 structures terminate transcription, called attenuation
2&3 hairpin structure allows for transcription to occur, called antitermination

Question 6

elements for attenuation

Answer 6

high levels of tryptophan
ribosome covers region 2 and doesn’t stall at trp codon
3&4 secondary structure
termination occurs

Question 7

elements for no attenuation

Answer 7

low levels of tryptophan
ribosome covers region 1 and does stall at trp codon
2&3 secondary structure
no termination occurs

Question 8

antisense RNA

Answer 8

RNA that can form a complement to the mRNA that is inhibitory to translation

Question 9

riboswitches

Answer 9

sequences within the mRNA that can fold to prevent ribosome binding

Question 10

ribozymes

Answer 10

catalytic RNA

in some cases mRNA sequences can form secondary structures that can autodegrade