2.2 Study Guide

Question 1

Why are alpha helices commonly found in DNA-binding proteins
a. Alpha helices more commonly have basic residues that interact with the DNA backbone
b. The width of an alpha helix fits perfectly in the minor groove of DNA
c. The width of an alpha helix fits perfectly in the major groove of DNA
d. Alpha helices are NOT commonly found in DNA-binding proteins

Answer 1

The width of an alpha helix fits perfectly in the major groove of DNA

Question 2

Which of these DNA-binding proteins binds to DNA using a saddle shaped beta sheet structure?
a. The TATA-box binding protein
b. p53
c. The lactose repressor
d. Cro
e. Zinc finger transcription factors

Answer 2

The TATA-box binding protein

Question 3

Which is TRUE about homeobox transcription factors?
a. They contain a zinc-finger domain
b. They bind E-box motifs in the DNA
c. They contain a recognition helix
d. They bind ONLY to the minor groove of DNA
e. They are oncogenes (mutations in them cause cancer)

Answer 3

They contain a recognition helix

Question 4

Which is TRUE about p53 structure?
a. p53 binds to DNA as a dimer
b. p53 contains a beta barrel, and contributes a beta strand to the SLH domain
c. p53 is a zinc-finger transcription factor
d. p53 does not interact with the DNA backbone
e. Lysine residues are critical for p53 function

Answer 4

p53 contains a beta barrel, and contributes a beta strand to the SLH domain

Question 5

Which structural features do zinc-finger transcription factors NOT contain?
a. A zinc ion
b. A beta strand
c. An alpha helix
d. A coiled-coil domain

Answer 5

A coiled-coil domain

Question 6

Which is a domain of leucine zipper transcription factors?
a. The zipper domain
b. The basic domain
c. The SLH domain
d. Both a and b
e. Both b and c

Answer 6

Zipper domain and basic domain

Question 7

How many alpha helices are in a helix-loop-helix transcription factor monomer?
a. 1
b. 2
c. 3
d. 4
e. 6

Answer 7

2

Question 8

Which is TRUE about the structure of Cro?
a. Cro binds to DNA as a monomer
b. Cro is composed of 5 alpha helices
c. Cro is a helix-loop-helix DNA binding protein
d. Cro binds to the lambda repressor promoter contained in the lambda phage operator region
e. None of the above

Answer 8

Cro binds to the lambda repressor promoter contained in the lambda phage operator region

Question 9

Which is NOT a function of lambda repressor?
a. Negative regulation of Cro transcription
b. Positive regulation of lambda repressor transcription
c. Positive regulation of lambda phage lysogeny
d. Nutrient sensing
e. All of these are functions of lambda repressor

Answer 9

Nutrient sensing

Question 10

Why does tryptophan binding change the ability of the Trp repressor to associate with DNA?
a. Tryptophan binding causes Trp repressor monomers to dimerize
b. Tryptophan binding causes the Trp repressor to be degraded
c. Tryptophan binding repositions the DNA-binding helices to be approx. 34 angstroms apart
d. Tryptophan binding repositions the DNA-binding helices to point at the wrong angle to bind DNA
e. Tryptophan binding does not affect Trp repressor association with DNA

Answer 10

Tryptophan binding repositions the DNA-binding helices to be approx. 34 angstroms apart

Question 11

Which is TRUE about the lactose repressor?
a. It changes conformation when lactose binds to it
b. Lactose-binding causes the repressor to dissociate from DNA
c. It is a tetramer
d. It causes a hairpin structure to form in the DNA
e. All of the above

Answer 11

All of the above