week 11: control of gene expression in prokaryotes

Question 1

housekeeping v regulated genes

Answer 1

• housekeeping genes are expressed continously because they are needed for cellular maintenance (like glucose metabolsim)
• these genes are switched on when needed and off to save energy and allow rapid responses to change in environment

Question 2

lac operon components

Answer 2

lac Z - B-galactosidase, converts lactose to glucose and galactose
lac Y - permease, allows entry of lactose into cells
lac A - transacetylase, removes toxic byproducts of lactose digestion

Question 3

negative regulation of lac operon

Answer 3

no lactose-> repressor binds to operator. no transcription
lactose -> lactose binds to R, forcing it to change shape and fall off O

Question 4

lactose but no glucose (+ reg)

Answer 4

1. low glucose induces adenylyl cyclase production
2. AC converts ATP->cAMP
3. cAMP binfs to CAP (catabolite activating protein)
4. the complex interacts with RNA polymerase
5. transcription happens/ high expression

Question 5

lactose and glucose (+ reg)

Answer 5

glucose metabolism reduces cAMP levels therefore CAP-cAMP complex levels as well. very low lac gene transcription

Question 6

no lactose

Answer 6

no expression

Question 7

examples of translational control

Answer 7

• riboswitches:
• antisense RNA

Question 8

post translational control

Answer 8

feedback inhibition - when product levels build up, the final product inhibits enzyme this the reaction pathway