Question 1

The backbone of nucleic acids consists of

Accepted Answer

A)  a phosphodiester bond between the 2' and 5' hydroxyl groups of neighboring sugars 
B)  a phosphodiester bond between the 3' and 5' hydroxyl groups of neighboring sugars 
C)  a glycosidic bond between a pyrimidine and a sugar 
D)  a glycosidic bond between a purine and a sugar

Question 2

The Z-form of DNA

Accepted Answer

A)  does not exist in nature. 
B)  is right-handed. 
C)  tends to occur in purine-only sequences. 
D)  tends to occur in pyrimidine-only sequences. 
E)  tends to occur in alternating purine-pyrimidine sequences.

Question 3

Propeller twists occur in B-DNA so that

Accepted Answer

A)  Z-DNA can form 
B)  base pairing distances are optimized 
C)  base stacking can better occur 
D)  none of these

Question 4

Which of the following bases is not found in RNA?

Accepted Answer

A)  A 
B)  C 
C)  G 
D)  T 
E)  All of these are found in RNA.

Question 5

Which of the following statements is true for double-stranded DNA?

Accepted Answer

A)  The amount of A is the same as the amount of T, and the amount of G is the same as the amount of C. 
B)  The amount of A is the same as the amount of G, and the amount of T is the same as the amount of C. 
C)  The amount of A is the same as the amount of C, and the amount of G is the same as the amount of T. 
D)  More than one of the above is true.

Question 6

Which of the following groups is not found in nucleosides?

Accepted Answer

A)  Phosphates 
B)  Purines 
C)  Pyrimidines 
D)  Sugars 
E)  All of these are found in nucleosides

Question 7

Which of the following best describes the structure of a nucleosome?

Accepted Answer

A)  DNA wrapped around an octomer containing two each of H2A, H2B, H3, and H4 with H1 on the outside. 
B)  DNA wrapped around an octomer of H1 with H2A,B, H3 & H4 on the outside. 
C)  DNA wrapped around a octomer of either H2A\H2B or H3\H4 with H1 on the outside. 
D)  DNA wrapped around a tetramer of either H2A\H2B or H3\H4 with H1 on the outside. 
E)  None of these

Question 8

Which of the following statements concerning the B-form of DNA is false ?

Accepted Answer

A)  It twists in a left-handed direction. 
B)  The distance between base pairs is 3.4Å. 
C)  The width of a base pair is about 1.1 nm. 
D)  The diameter, including the phosphate, is about 20 Å.

Question 9

Two circular DNAs are isolated, both with 1000 bp. One is supercoiled; the other is not. The two DNAs are placed in an ultracentrifuge.

Accepted Answer

A)  The supercoiled DNA should sediment faster. 
B)  The nonsupercoiled DNA should sediment faster. 
C)  They should sediment at the same rate. 
D)  The information provided is not enough to determine which will sediment faster.

Question 10

Which of the following is the most common modification of nucleic acid bases?

Accepted Answer

A)  addition of a methyl group 
B)  addition of a carboxylic acid 
C)  addition of a fluorine 
D)  reduction of a carbonyl to an alcohol

Question 11

Which of the following can be an epigenetic change to chromatin?

Accepted Answer

A)  methylation 
B)  acetylation 
C)  phosphorylation 
D)  All of these 
E)  None of these

Exam 9: Nucleic Acids How Structure Conveys Information