gene regulation in bacteria

Question 1

how does the Lac-z suppressor work?

Answer 1

Lac gene suppressor works on a Helix-turn-helix motif of the repressor fits into the major groove of DNA and makes contact with bases. Each tetramer binds two operator sequences. This prevents RNA pol from initiating but it can still bind

Question 2

how does the lac operon work

Answer 2

LacZ is suppresor binds to operator region stops transcription
Allolactose produced by beta-galactosidase binds top supressor decresing its affinity for the carbon chain

Question 2

how does the lac operon work

Answer 2

LacZ is suppresor binds to operator region stops transcription
Allolactose produced by beta-galactosidase binds top suppressor decreasing its affinity for the carbon chain
enabling the transcription of beta galactosidease

Question 3

whay effects does a high glucose concentration have on Lac operon functioning

Answer 3

high glucose=low cAMP

RNA pol cannot bind to the premotor

Question 4

what does ribosome efficiency regulate

Answer 4

amount of protein produced

Question 5

what prevents transcription of TrpL in high tryptophan enviroments

Answer 5

When tryptophan (and therefore charged tRNATrp) is abundant, the translating ribosome completes synthesis of the leader peptide. The ribosome position prevents formation of base pairs between RNA sequences 2 and 3 of the mRNA. This allows formation of a stem-loop involving complementary sequences 3 and 4, and NusA-dependent termination of transcription.

Question 6

how do low levels of tryptophan enable TrpL transcription

Answer 6

When tryptophan (and therefore charged tRNATrp) is limiting, the translating ribosome becomes stalled at two consecutive Trp codons on the mRNA. Ribosome stalling now allows formation of base pairs between RNA sequences 2 and 3. The NusA-dependent terminator stem-loop cannot form, so transcription continues into the structural genes.