Question

Question 28:

A system in which a regulatory protein binding to a co-regulatory molecule causes it to leave the operator, thereby inhibiting transcription of target genes, an example of:

Group of answer choices

a. Inducible negative control

b. Repressible positive control

c. Inducible positive control

d. Repressible negative control

Question 29:

MEK, a MAP kinase kinase, is activated by phosphorylation. You create a mutant MEK in which the amino acids that are normally phosphorylated is replaced with aspartate. Predict the impact of this change on MEK activity.

Group of answer choices

a. Always inactive

b. Always active

c. No change

Answer 1

28. Correct answer: b, Repressible positive control. In positive repressible operons the activator proteins are normally bound to the pertinent DNA segment. However, when an inhibitor is bound by the activator, it is prevented from binding to DNA thus inhibiting the transcription.

29. Correct answer: a, always inactive. MEK has amino acids that when phosphorylated open the catalytic core of Mitogen activated kinase kinase enzyme. On phosphorylation of these amino acids the MEK becomes active. So when these amino acids when are replaced by aspartate MEK would remain always inactive.