Lecture 21/22

Question 1

What are I+, I(s) I- mutations with regards to the lac operon?

Answer 1

I stands for the inducer, with I+ functioning normally and I- being mutation in which the repressor can not bind to the DNA resulting in lactose gene transcription
I+ is dominant to I- in a trans position
I(s) destroys the inducer region of the repressor and will result in the lactose gene not being transcribed even in the presence of lactose
I(s) is dominant to I+ in trans

Question 2

What are the O+ and Oc alleles in the lac operon?

Answer 2

O is the operater region to which the repressor binds, O+ is normal wild type
Oc is a mutation where the repressor is unable to bind leading to lactose gene transcription Oc is dominant to O+ in cis

Question 3

How do promoter mutations function in the lac operon?

Answer 3

Mutations to the promoter are cis dominant