Deck 4: Nucleic Acids

Question 1

Single-stranded RNA molecules can have extensive regions of intramolecular base pairing leading to defined secondary and tertiary structure.

Answer 1

True

Question 2

Supercoiled DNA has a lower mobility than relaxed DNA with the same number of base pairs when subjected to gel electrophoresis.

Answer 2

False

Question 3

The melting temperature of DNA ________ with increasing G plus C content.

Answer 3

increases

Question 4

Which of the following statements about nucleic acid secondary structure is FALSE?

A) The width of the major and minor grooves is more equal in the A-from of DNA than in the B-form.
B) Triple helices and G-quadruplexes can form at specific sequences in DNA.
C) DNA can form cruciform structures at palindromic sequences.
D) The A-form of DNA exists at high humidity, whereas the B-form exists at low humidity.
E) Some nucleic acids can form a zig-zag structure or Z form.

Question 5

The mode of replication of DNA is BEST described as ________.

Question 6

Restriction endonucleases are useful in gene cloning because:

A) they can cut DNA at specific sequences.
B) they can join DNA molecules that have been cut at specific sequences.
C) they all make cohesive ends when they cut DNA.
D) they all make 5' phosphate extensions and recessed 3' OH groups that can be rejoined by DNA ligase.
E) they can both cut and rejoin DNA molecules.

Question 7

An important observation that assisted in the elucidation of the secondary structure of DNA was that the mole percent adenine was almost always the same as the mole percent of thymine.

Question 8

Which of the following does NOT describe the secondary structure of DNA as proposed by Watson and Crick?

A) The two strands of the double helix are stabilized by hydrogen-bonding between A and T and between G and C.
B) The two strands of the double helix run in opposite directions.
C) The distance between the 1' carbons of the deoxyribose units is the same between the A-T and the G-C base pair.
D) The phosphate deoxyribose backbones of the helix are on the outside.
E) The base pairs are stacked on one other with their planes at 180o to the helix axis.

Question 9

Nucleotides are all weak acids.

Question 10

Expression of genetic information involves first ________ then ________.

Question 11

Dideoxynucleotide sequence analysis is a template-directed method that makes use of chain terminators that stop DNA synthesis because they lack a 2'OH group.

Question 12

Which statement is CORRECT?

A) Both phosphodiester and glycosidic bonds in RNA and DNA are hydrolyzed in acid solution.
B) Both RNA and DNA are hydrolyzed in mild alkaline solution.
C) DNA is more unstable when dehydrated than when in solution
D) RNA is not hydrolyzed in mild alkaline solution.
E) Both A and B

Question 13

Calculate the linking number in vivo for a plasmid that is 4200 bp in size if there is normally 1 negative supercoil in every 20 base pairs of a circular DNA. Assume there are 10.5 bp per turn of the double helix.

Question 14

Nucleic acids absorb light strongly in the ultraviolet region of the spectrum because they have ________ double-bond systems.

Question 15

The difference between a nucleoside and a nucleotide is:

A) the presence of uracil.
B) a phosphate group.
C) a phosphodiester bond.
D) a 2' -H group.
E) methylated cytosine.

Question 16

The nucleotide sequence of a polynucleotide chain is called the ________ structure.

Question 17

DNA in vivo is normally ________ supercoiled.

Question 18

Viral genomes cannot be used as vectors for making recombinant DNA molecules.

Question 19

Calculate the superhelix density of a circular DNA molecule with 210 base pairs and two negative supercoils, assuming that there are 10.5 bp per turn of the double helix.

Question 20

Which of the following is a feature of X-diffraction?

A) Radiation passing through a structure will be scattered only if the structure contains repeating units.
B) Scattered radiation from repeating units in a structure will be weakened by interference.
C) Scattered radiation from repeating units in a structure will be strengthened by interference.
D) Short spacings in repeating structures will result in short spacings in diffraction patterns.
E) The wavelength of radiation used to generate diffraction patterns must be slightly longer than the spacings between the repeating units of the structure.