Deck 9: Nucleic Acids: How Structure Conveys Information

Question 1

What distinguishes nucleotides from nucleosides?

A) Nucleosides lack the phosphate group.
B) Nucleosides lack the sugar group.
C) Nucleosides lack a nitrogenous base.

Answer 1

A

Question 2

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

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.

Answer 2

A

Question 3

Deoxyadenylate (dA) is a:

A) purine base
B) pyrimidine base
C) purine based nucleoside
D) purine based nucleotide

Answer 3

D

Question 4

Histones are proteins that

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 5

The double helix of DNA is which level of structure?

A) primary
B) secondary
C) tertiary
D) quaternary

Question 6

Where can drugs or polypeptides bind to DNA?

A) The minor groove only.
B) The major groove only.
C) Either the minor or major groove.
D) Neither the minor or major groove.

Question 7

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

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 8

The outside diameter of a piece of DNA is closest to

A) 2 Å.
B) 20 Å.
C) 200 Å.
D) 2000 Å.

Question 9

Which of the following nucleobases is a purine?

A) adenine
B) cytosine
C) thymine
D) uracil

Question 10

Which contains a phosphoanhydride bond?

A) DNA
B) RNA
C) ATP
D) AMP

Question 11

Which of the following groups is not found in nucleosides?

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

Question 12

The nucleotide sequence of DNA is which level of structure?

A) primary
B) secondary
C) tertiary
D) quaternary

Question 13

Which is the dominant form of DNA found in the cell?

A) A
B) B
C) Z
D) H

Question 14

The backbone of nucleic acids consists of

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 15

The oligonucleotide AGGUCCAUUGAAp,is best described as

A) an RNA oligonucleotide with a 3'phosphate
B) an RNA oligonucleotide with a 5'phosphate
C) a DNA oligonucleotide with a 3'phosphate
D) a DNA oligonucleotide with a 5'phosphate

Question 16

The fundamental differences between RNA and DNA are

A) the organic bases only
B) bases, ribose units, and the phosphodiester linkage
C) bases, ribose units, and the glycosidic bond type
D) bases and the ribose units only

Question 17

Which of the following bases is not found in RNA?

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

Question 18

Quaternary structure refers to the non-covalent interaction(s) between polymeric units,such as two or more monomer protein units that noncovalently interact.Which of the following scenarios for nucleic acids most closely resembles quaternary structure?

A) self-assembly of subunits in the tobacco mosaic virus
B) interaction of DNA with proteins
C) RNA and protein association in ribosomes
D) All of these

Question 19

Which best describes the relationship between the nucleobases in a piece of DNA?

A) They are parallel to the helical axis.
B) They are perpendicular to the helical axis.
C) They are randomly oriented with respect to the helical axis.

Question 20

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

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 21

Which piece of DNA will have the higher T_m,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?

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

Question 22

The three dimensional structure of nucleic acids can include all except:

A) Supercoiling
B) Base stacking
C) Hairpin loops
D) Circular molecules
E) All of these can be included in the three dimensional structure

Question 23

Propeller twists occur in B-DNA so that

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

Question 24

The strands in the double helix

A) both run in the same 3' 5' direction, i.e., they are parallel.
B) have their 3' 5' directions opposed, i.e., they are anti-parallel.
C) can be either parallel or anti-parallel.
D) are perpendicular to one another.

Question 25

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

Question 26

Base pairs with a propeller-twist

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

Question 27

Hydrophobic bonding via pi-clouds is referred to as

A) base stacking.
B) propeller twist.
C) hyperchromicity.
D) supercoiling.

Question 28

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

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

Question 29

Topoisomerases are associated with

A) production of RNA from DNA.
B) joining of nucleotide monomers to make polynucleotides.
C) supercoiling of DNA.
D) ribosomes.

Question 30

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

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

Question 31

The human genome has 3 × 10⁹ base pairs (bp) of DNA If this were one continuous molecule and extended such that each nucleotide was separated from the adjacent nucleotide by 4 Å,as proposed in the Watson and Crick model,what would the end-to-end distance be?

A) 1 meter
B) 1 centimeter
C) 1000 centimeters
D) 10¹⁴ Å

Question 32

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

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 33

Calculate the length/diameter ratio for the extended E.coli DNA (4 Å between adjacent nucleotides).

A) 4 × 10⁵
B) 1 × 10⁵
C) 3 × 10⁸
D) 3 × 10⁶

Question 34

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

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 35

The A and B forms of DNA

A) both have 10 base pairs per turn of the helix
B) both have 11 base pairs per turn of the helix
C) are both left-handed helices
D) are both right-handed helices

Question 36

Which conclusion can be drawn from the experimental observation that a single strand of DNA contains 2100 dA residues and 1800 dT residues?

A) There must have been some loss of material in the extraction because the number of dA and dT residues must be the same.
B) This is a palindromic sequence.
C) There must be 2100 dT and 1800 dA residues on the complementary strand.
D) none of these

Question 37

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

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 38

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

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.

Question 39

The Z-form of DNA

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 40

Supercoiling of DNA

A) is not observed in prokaryotes
B) requires the action of topoisomerase enzymes
C) does not require ATP
D) is not observed in eukaryotes

Question 41

Which of the following is not true?

A) The amount of UV absorbance increases, but the wavelength does not change as DNA nears its melting point
B) Once DNA is denatured, it cannot renature
C) The melting temperature partially depends on the GC content
D) The nature of the solvent the DNA is in can affect the melting temperature

Question 42

Transfer RNA molecules are characterized by all the following,except:

A) They are one of the largest of the RNAs.
B) Cloverleaf shape.
C) Many modified bases.
D) Extensive secondary and tertiary structure.
E) All of these characterize transfer RNA molecules.

Question 43

Which of the following modifications is likely to happen to the mRNA in a eukaryotic cell?

A) capping of the 5' end
B) addition of a poly-A tail to the 3' end
C) removal of intervening sequences (introns)
D) All of the above occur in eukaryotic cells.

Question 44

The T_m for melting the double helix is:

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 45

The study of DNA changes that are not reflected in the base sequence is called:

A) Molecular biology
B) Histology
C) Epigenetics
D) Physical genetics

Question 46

The three-dimensional structure of transfer RNA has been determined by

A) analytical ultracentrifugation
B) gel electrophoresis
C) ultraviolet spectroscopy
D) x-ray crystallography

Question 47

The hydrogen bonding interactions in a Watson-Crick AT base-pair involve what units in the adenine base?

A) N-1 and the amino group on C-6
B) N-1 and N-3
C) N-7 and the amino group on C-6
D) N-7 and C-8

Question 48

In a melting profile for DNA,the absorbance at 260 nm increases as result of the disruption of the DNA structure.What is the fundamental physical basis for the absorbance increase?

A) the effective concentration of DNA changes
B) denatured DNA absorbs light more strongly than native DNA because the bases have become unstacked
C) native DNA absorbs light more strongly than denatured DNA because the bases are stacked
D) the absorbance of DNA is highly sensitive to temperature

Question 49

RNA is hydrolyzed in basic solution,but DNA is not.This occurs because

A) thymine is found in DNA, and uracil is not
B) DNA is double stranded, and RNA is single stranded
C) DNA contains 2'-deoxyribose, but RNA does not
D) RNA has modified bases, but DNA does not

Question 50

Which of the following statements concerning transfer RNA is true?

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 51

Which of the following RNAs is the least abundant in a typical cell?

A) mRNA
B) rRNA
C) snRNA
D) tRNA

Question 52

Eukaryotic and prokaryotic ribosomes can be compared in all these ways,except:

A) Both have large and small subunits.
B) Eukaryotic ribosomes are larger.
C) Both contain the same number of RNA molecules.
D) Eukaryotic ribosomes contain more proteins.
E) All of these statements are accurate comparisons.

Question 53

Eukaryotic mRNA requires

A) less processing after synthesis than prokaryotic mRNA.
B) more processing after synthesis than prokaryotic mRNA.
C) about the same amount of processing after synthesis as prokaryotic mRNA.

Question 54

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

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

Question 55

The most recent discoveries in RNA research are:

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

Question 56

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

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

Question 57

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

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

Question 58

Which of the following statements concerning small nuclear RNA is true?

A) This RNA is usually found in snurps.
B) This RNA is involved in removing exons from the RNA.
C) This RNA was the first RNA shown to have catalytic activity.
D) This RNA is small in size.
E) All of these describe small nuclear RNA.

Question 59

Which of the following statements concerning ribosomes is true?

A) They consist of two RNA subunits, one of which is larger than the other.
B) They contain both RNA and protein.
C) They can be dissociated and reassembled by controlling the Mg²⁺ concentration of the medium.
D) All of these are true.

Question 60

The melting profile for a DNA is found to differ in two different salt solutions.In 0.001 M NaCl,T_m = 55 C,and in 0.01 M NaCl,T_m = 65

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