The Operon Part 1 (6)

Front 1

A strain of E. coli has two copies of the lac operon: one in the chromosome and the other on a plasmid. You observe that when you grow up one of the colonies that it produces half as much of all of the proteins encoded by the lac operon when glucose is absent and lactose is present (the operon should be ON). Which of the following statements is the most likely explanation of these results?

Back 1

A mutation occurred in the core promoter (-10 or -35 sites) of one of the two operons.

Front 2

Which protein or domain within bacterial RNA polymerase contacts DNA using minor groove contact?

Back 2

The CTD of the alpha subunit

Front 3

Which of the following represent the association constant of a DNA binding protein?

Back 3

[free repressor-DNA complex]/[free repressor] x [total cellular DNA]

Front 4

The Lac repressor bound to IPTG prefers Operator DNA 10,000 times more than non-Operator DNA.

Back 4

True

Front 5

The Lac repressor is present in only 10 copies per cell in E. coli. Why is this so?

Back 5

The promoter has a very poor match to the Sigma 70 consensus, and the mRNA has a very short 5’-UTR (untranslated region).

Front 6

Which of the following pathways are regulated by repression caused by the accumulation end-product?

Back 6

Tryptophan biosynthesis

Front 7

In the diagram of the Lac repressor shown below, which number corresponds to region of the protein containing leucine zippers and is responsible for holding the dimers together?

Back 7

Number 3

Front 8

In the diagram of the Lac repressor shown below, which number corresponds to a DNA binding domain (“hinge helix”) that interacts with the minor groove of the Operator site?

Back 8

2

Front 9

In the diagram of the Lac repressor shown below, which number corresponds to a DNA binding domain that interacts with the major groove of the Operator site?

Back 9

1

Front 10

At the promoter for the lac operon, how does the DNA loop block transcription?

Back 10

by creating torsional strain in the DNA at the promoter which prevents the transition from closed to open promoter complex.

Front 11

Which statement is TRUE regarding the operon promoter shown in the figure below?

Back 11

This is an example of Positive Control

Front 12

filler

Back 12

filler