lecture 8

Question 1

regulation feedbacks

Answer 1

• gene expression precisely regulated in response to environmental conditions
• cell regulate enzyme activity by feedback inhibition/gene regulation
• feedback inhibition = enzyme’s activity is inhibited by enzymes end product
• gene regulations = process of turning genes on and off

Question 2

operon model

Answer 2

• one mechanism control gene expression (bacteria)
• cluster of functionally related genes coordinately controlled by sing ‘on-off switch’
• switch is segment DNA (operator) located within promoter
• operon = entire stretch of DNA (including operator; promoter; genes controlled)

Question 3

trp operon

Answer 3

• operon switched off by protein repressor (prevent transcription; binds to operator blocking RNA polymerase)
• repressor is product og separate regulatory gene (located distance from operon itself)
• absences of co-repressor (tryptophan); repressor is inactive (tryptophan operon switched on)
• presence of co-repressor; repressor activated and switch turned off

Question 4

other mechanisms of gene regulation in bacteria

Answer 4

• trp operon is repressible = operon ‘on’ in absence of co-repressor (repressor protein inactive)
• other operons is inducible = opern ‘off in absence of active co-repressor
• both operons example of negative gene regulation
• gene regulation more complicated for eukaryotes (promoters play key role)