Question 1

The most recent discoveries in RNA research are:

Accepted Answer

A)   mRNA and tRNA
B)   MiRNA and SiRNA
C)   snRNA and snurps
D)   tRNA and MiRNA B

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. E

Question 3

The helix can be untwisted by the action of which type of topoisomerase?

Accepted Answer

A)   Type I only
B)   Type II only
C)   Both types I and II
D)   Topoisomerases cannot untwist the helix. C

Question 4

The Tm for melting the double helix is:

Accepted Answer

A)   The temperature at which the helix starts to open.
B)   The midpoint of the range over which the helix denatures.
C)   The temperature at which the helix is completely open.
D)   The energy needed to melt the DNA.
E)   None of these is correct.

Question 5

In analytical ultracentrifugation the sedimentation coefficient,which is expressed in Svedberg units (S),characterizes a sedimenting particle on the basis of

Accepted Answer

A)   size only
B)   shape only
C)   both size and shape
D)   neither size nor shape

Question 6

Which of the following statements concerning transfer RNA is true?

Accepted Answer

A)   It has the highest molecular weight of the commonly occurring forms of RNA.
B)   It has no internal hydrogen bonding.
C)   It bonds to amino acids in the course of protein synthesis.
D)   All of these are true.

Question 7

Histones are proteins that

Accepted Answer

A)   are frequently associated with eukaryotic DNA
B)   are frequently associated with prokaryotic DNA
C)   are never found in association with DNA
D)   contain a high percentage of residues with carboxylic acid side chains

Question 8

Which of the following sequences of DNA is most likely to form Z-DNA?

Accepted Answer

A)   5'-ATCTACATCTACATAGATAT-3'3'-TAGATGTAGATGTATCTATA-5'
B)   5'-AAAAAAAAAAAAAAAAAAAA-3'3'-TTTTTTTTTTTTTTTTTTTT-5'
C)   5'-GCGCGCGCGCGCCGCGCGCG-3'3'-CGCGCGCGCGCGCGCGCGCG-5'
D)   5'-GGGGGGGGGGGGGGGGGGGG-3'3'-CCCCCCCCCCCCCCCCCCCC-5'

Question 9

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 10

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 11

Protein synthesis can occur while the mRNA molecule is being synthesized in:

Accepted Answer

A)   Prokaryotes only.
B)   Eukaryotes only.
C)   Unicellular organisms only.
D)   Multicellular organisms only.

Question 12

The melting profile for a DNA is found to differ in two different salt solutions.In 0.001 M NaCl,Tm = 55° C,and in 0.01 M NaCl,Tm = 65°C. The fundamental reason for this change is

Accepted Answer

A)   higher salt concentration increases the electrostatic repulsions between phosphates
B)   the base stacking is more effective in high salt
C)   hydrogen bonding between complementary bases in enhanced at high salt
D)   higher salt concentration decreases the electrostatic repulsions between phosphates

Question 13

Which of the following characteristics is associated with the B form of DNA?

Accepted Answer

A)   the sugars are located in the interior of the double helix
B)   the distance between base pairs along the axis of the helix is 8 Å
C)   the major and minor grooves are readily apparent
D)   the planes of the bases make about a 20 degree angle with the helix axis

Question 14

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 15

Which piece of DNA will have the higher Tm,one with a cytosine plus guanine content of 30% or one with a cytosine plus guanine content of 50% if both are heated under the same experimental conditions?

Accepted Answer

A)   30% cytosine plus guanine will have the higher Tm.
B)   50% cytosine plus guanine will have the higher Tm.
C)   Their Tm's will be the same.
D)   There's no way to predict for this information.

Question 16

The following types of RNA are common to all organisms,except:

Accepted Answer

A)   mRNA
B)   rRNA
C)   snRNA
D)   tRNA
E)   All types are found in all organisms.

Question 17

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 18

Histones contain large amounts of which of the following amino acids?

Accepted Answer

A)   histidine
B)   glutamic acid
C)   lysine
D)   leucine
E)   tryptophan

Question 19

Comparison of DNA sequences between widely diverse organisms indicates that all organisms have genetic similarity.

Accepted Answer

A) True 
 B)False

Question 20

Base pairs with a propeller-twist

Accepted Answer

A)   are found only in Z-DNA
B)   have optimum base stacking
C)   bind water in the minor groove
D)   have stronger hydrogen bonds than base pairs without a propeller twist

Exam 9: Nucleic Acids: How Structure Conveys Information