BCCB2000 Lecture 12 Questions

Question 1

The number of glycosidic bonds in a nucleotide triphosphate is ___________

Answer 1

1

Question 2

The DNA oligonucleotide abbreviated pATCGAC: A. has a phosphate on its 3’ end. B. has an A at its 3’ end. C. has 6 phosphate groups. D. violates Chargaff’s rules.

Answer 2

C. has 6 phosphate groups

Question 3

RNA is an abbreviation for [a] acid.

Answer 3

ribonucleic

Question 4

Purines and pyrimidine bases in DNA are molecules that have: A. intermolecular hydrogen bonds B. both hydrogen bond acceptors and donors C. only hydrogen bond acceptors D. only hydrogen bond donors E. intramolecular hydrogen bonds

Answer 4

A. intermolecular hydrogen bonds B. both hydrogen bond acceptors and donors

Question 5

Chargraff’s rules states that: A. The amount of adenine equals the amount of thymine B. The amount of adenine equals the amount of cytosine C. The amount of purines equals the amount of pyrimidines D. The amount of guanine equals the amount of thymine E. The amount of guanine equals the amount of cytosine

Answer 5

A. The amount of adenine equals the amount of thymine C. The amount of purines equals the amount of pyrimidines E. The amount of guanine equals the amount of cytosine

Question 6

Compounds that contain a nitrogenous base and a pentose sugar are called [a]

Answer 6

nucleoside

Question 7

For the oligoribonucleotide pACGUAC: A. the nucleotide at the 5’ end is a pyrimidine. B. the nucleotide at the 3’ end has a phosphate at its 3’ hydroxyl. C. the nucleotide at the 5’ end has a phosphate on its 5’ hydroxyl. D. All of the above are true. E. None of the above is true.

Answer 7

C. the nucleotide at the 5’ end has a phosphate on its 5’ hydroxyl.

Question 8

The nucleotide sequence has little or no effect on which form (A, B, or Z) DNA will take. True or False?

Answer 8

False

Question 9

Nucleotides are important as: A. energy carriers B. cofactors or coenzymes C. precursors of nucleic acid D. components of membranes E. components of proteins F. signalling molecules

Answer 9

A. energy carriers B. cofactors or coenzymes C. precursors of nucleic acid F. signalling molecules

Question 10

There are estimated to be about 1013 cells in the human body (not counting bacteria). Estimate the length of DNA from all cells in the human body assuming that all cells are diploid (i.e.23 pairs of chromosomes) and that all of the DNA is in the B-form. A. 2.0 x 1012 m B. 1.0 x 1013 m C. 2.0 x 1013 m D. 4.0 x 1013 m

Answer 10

C. 2.0 x 1013 m

Question 11

Which of the following descriptions applies to the A-form of DNA? A. left-handed, long and thin, 4.0 A and 13 bp per turn. Found in AT rich regions B. left-handed, long and thin, 3.8 A and 12 bp per turn. Found in GC rich regions C. right-handed, long and thin, 3.32 A and 10 bp per turn. Usual in vivo conformation D. right-handed, short and broad, 2.3 A and 11 bp per turn. Found in dehydrated, non-physiological conditions

Answer 11

D. right-handed, short and broad, 2.3 A and 11 bp per turn. Found in dehydrated, non-physiological conditions

Question 12

What is the approximate total length of B-DNA (in metres) in the human diploid genome if there are 3 x 109 base pairs in the human haploid genome? A. 0.5 m B. 1.0 m C. 2.0 m D. 3.0 m

Answer 12

C. 2.0 m 0.34 x 10-9 m (i.e. 0.34 nm or 3.4 Å) vertical spacing between subsequent base pairs in human DNA space between base pairs x number of base pairs in DNA x 2 (for diploid genome) = length of DNA 0.34 x 10-9 m x 3 x 109 base pairs x 2 = 2.04 = 2.0 m (2 sig fig)

Question 13

The polymer (5’)GTGATCAAGC(3’) could form a double-stranded structure with: A. (5’)CACUTTCGCCC(3’). B. (5’)GCTTGATCAC(3’). C. (5’)CACTAGTTCG(3’). D. (5’)GCCTAGTTUG(3’). E. (5’)CACUAGUUCG(3’).

Answer 13

B. (5’)GCTTGATCAC(3’).

Question 14

Which of the following is correct for RNA: A. Adenosine-Thymine base pairs share three hydrogen bonds B. ribose units are connected by 3’,5’ phosphoanhydride bonds C. phosphate groups project toward the middle of the double helix D. hydrogen bonds form between complementary base pairs

Answer 14

D. hydrogen bonds form between complementary base pairs

Question 15

In the Watson-Crick model of DNA structure (now called B-form DNA): A. A-T pairs share three hydrogen bonds. B. a purine in one strand always hydrogen bonds with a purine in the other strand. C. G-C pairs share two hydrogen bonds. D. the 5’ ends of both strands are at one end of the helix, and both 3’ ends are at the other end of the helix. E. the bases occupy the interior of the helix

Answer 15

E. the bases occupy the interior of the helix

Question 16

Two purines found in DNA are_____________and _____________

Answer 16

Adenine, Guanine

Question 17

The two pyrimidines found in RNA are_____________and _____________

Answer 17

Cytosine and Uracil

Question 18

If the hydroxyl group attached to the 2’ carbon of ribose existed in DNA it would tend to disrupt the relatively stable helix of DNA. True or False?

Answer 18

True

Question 19

If a carbon was labeled 5’ in a nucleoside then this would indicate that the carbon belonged to: A. the hexose sugar B. the purine base C. the pyrimidine base D. the phosphodiester backbone E. the pentose sugar

Answer 19

E. the pentose sugar

Question 20

The hydroxyl group at the 2’ carbon position of the [a] sugar makes [b] relatively less stable than [c] because it is prone to a [d] reaction.

Answer 20

Specified Answer for: a ribose Specified Answer for: b RNA Specified Answer for: c DNA Specified Answer for: d hydrolysis

Question 21

A-form and B-form DNA are right handed helices but Z form DNA is a left handed helix found only in single stranded DNA. True or False?

Answer 21

False

Question 22

Which of the following descriptions applies to the B-form of DNA? A. right-handed, short and broad, 2.3 A and 11 bp per turn. Found in dehydrated, non-physiological conditions B. right-handed, long and thin, 3.32 A and 10 bp per turn. Usual in vivo conformation C. left-handed, long and thin, 4.0 A and 13 bp per turn. Found in AT rich regions D. left-handed, long and thin, 3.8 A and 12 bp per turn. Found in GC rich regions

Answer 22

B. right-handed, long and thin, 3.32 A and 10 bp per turn. Usual in vivo conformation

Question 23

RNA doesn’t usually exist as a double helix, like DNA, but you would expect some secondary structure to form because: A. Guanine and Uracil would form hydrogen bonds with each other in the RNA structure B. The hydrophobic bases would try to minimise their contact with water C. Adenosine and thymine would form hydrogen bonds with each other in the RNA structure D. The phosphodiester backbone of RNA would try to minimise its contact with water

Answer 23

B. The hydrophobic bases would try to minimise their contact with water

Question 24

Compounds that contain a nitrogenous base, a pentose sugar, and a phosphate are called [a]

Answer 24

nucleotide

Question 25

Nucleic acid samples have been isolated from four different organisms. The nucleic acids have the following composition (%): Sample 1: A=17; T=17; U=0; G=33; C=33 Sample 2: A=24; T=0; U=16; G=24; C=36 Sample 3: A=29; T=19; U=0; G=22; C=30 Sample 4: A=24; T=0; U=24; G=36; C=16 Which DNA sample would be expected to have the highest Tm (melting point)? A. Sample 1 B. Sample 2 C. Sample 3 D. Sample 4

Answer 25

A. Sample 1 There are three hydrogen bonds in this base pair and it would take more energy to break these bonds. Consequently, if the DNA had a relatively high G+C content, compared with the A+T content, then this would lead to a high Tm (melting point). The ratio A+T/G+C can estimate the content of G+C relative to A+T. The lower the ratio the higher the G+C content and the higher the Tm. In this case Sample 1 is DNA and the A+T/G+C = 34/66 = 0.5 hence the Tm would be higher in this sample compared with sample 3. Sample 2 is RNA not DNA Sample 3 is DNA and the A+T/G+C = 48/52 = 0.9 Sample 4 is RNA not DNA

Question 26

The size of a purine molecule is [a] when compared with a pyrimidine molecule

Answer 26

larger

Question 27

Which of the following could be components of guanylate: A. ribose B. deoxyguanine C. phosphate D. guanosine E. hexose F. guanine

Answer 27

C. phosphate D. guanosine F. guanine

Question 28

The phosphodiester bonds that link adjacent nucleotides join: A. the 2 hydroxyl of one nucleotide to the 3 hydroxyl of the next nucleotide B. the 3' hydroxyl of one nucleotide to the 5' hydroxyl of the next nucleotide C. the 2' hydroxyl of one nucleotide to the 3' hydroxyl of the next nucleotide D. the 3 hydroxyl of one nucleotide to the 5 hydroxyl of the next nucleotide

Answer 28

B. the 3' hydroxyl of one nucleotide to the 5' hydroxyl of the next nucleotide

Question 29

Both DNA and RNA contain a: A. hexose monosaccharide B. hexose disaccharide C. pentose disaccharide D. pentose monosaccharide

Answer 29

D. pentose monosaccharide

Question 30

In double-stranded DNA: A. the two strands are parallel. B. sequences rich in A-T base pairs are denatured less readily than those rich in G-C pairs. C. the structure is compatible only with a right-handed (never a left-handed) helix. D. the two strands have complementary sequences. E. the sequence of bases has no effect on the overall structure.

Answer 30

D. the two strands have complementary sequences.

Question 31

When double-stranded DNA is heated at neutral pH, which change does not occur? A. The absorption of ultraviolet (260 nm) light increases. B. The covalent N-glycosidic bond between the base and the pentose breaks. C. The hydrogen bonds between A and T break. D. The viscosity of the solution decreases. E. The helical structure unwinds.

Answer 31

B. The covalent N-glycosidic bond between the base and the pentose breaks.

Question 32

In DNA the purine and pyrimidine bases are stacked_________to each other

Answer 32

parallel

Question 33

What is the approximate total length of B-DNA (in metres) that has 3 x 109 base pairs in the human haploid genome (i.e. egg and sperm cells)? A. 0.5 m B. 1.0 m C. 2.0 m D. 3.0 m

Answer 33

B. 1.0 m

Question 34

Which of these statements about alternate forms of DNA is false? A. Z-form DNA has a helical sense (left-handed) that is opposite that for A-form DNA. B. Nucleotide sequence has little or no effect on which form DNA takes. C. B-form DNA predominates in aqueous solution; dehydration favors the A form. D. Short stretches (tracts) of Z-form DNA may play a role in the regulation of gene expression.

Answer 34

B. Nucleotide sequence has little or no effect on which form DNA takes.

Question 35

Which of the following descriptions applies to the Z-form of DNA? A. left-handed, long and thin, 3.8 A and 12 bp per turn. Found in GC rich regions B. left-handed, long and thin, 4.0 A and 13 bp per turn. Found in AT rich regions C. right-handed, short and broad, 2.3 A and 11 bp per turn. Found in dehydrated, non-physiological conditions D. right-handed, long and thin, 3.32 A and 10 bp per turn. Usual in vivo conformation

Answer 35

A. left-handed, long and thin, 3.8 A and 12 bp per turn. Found in GC rich regions

Question 36

DNA is an abbreviation for [a] acid.

Answer 36

deoxyribonucleic

Question 37

A major component of RNA but not of DNA is

Answer 37

Uracil

Question 38

What is the approximate length (in nm) of a DNA molecule (in the B form) containing 10,000 base pairs? A. 340 nm B. 3400 nm C. 34,000 nm D. 340,000 nm

Answer 38

B. 3400 nm vertical distance (spacing) between one base pair and the next base pair in a helix = 0.34nm 10,000 x 0.34 = 3,400 nm

Question 39

The base pair Adenine-Thymine (A-T) has _____ hydrogen bonds within the structure of DNA

Answer 39

2

Question 40

What is the approximate total length of B-DNA (in metres) in the mouse haploid genome that has 2.7 x 109 base pairs ?

Answer 40

0.92 space between base pairs x number of base pairs in DNA = length of DNA 0.34 x 10-9 m x 2.7 x 109 base pairs = 0.918 = 0.92 m (2 sig fig)

Question 41

Double-stranded regions of RNA: A. can be observed in the laboratory, but probably have no biological relevance. B. are less stable than double-stranded regions of DNA. C. can form between two self-complementary regions of the same single strand of RNA. D. have the two strands arranged in parallel (unlike those of DNA, which are antiparallel). E. do not occur.

Answer 41

C. can form between two self-complementary regions of the same single strand of RNA.