Deck 25: Structure of Nucleic Acids

Question 1

Which of the following statements is NOT correct regarding the linking number?

A)It is a basic parameter characterizing supercoiled DNA.
B)L = T + W.
C)It is the number of times that 2 strands are intertwined,providing both strands remain covalently intact.
D)L = 40 in a relaxed circular DNA duplex of 400 bp.

Answer 1

D

Question 2

Which of the following is a characteristic of in vitro DNA synthesis?

A)DNA polymerase adds nucleotides in a 3'?5' direction.
B)Correct hydrogen bonding is the primary check of the newly synthesized DNA.
C)The primer strand of DNA determines the nucleotides added.
D)DNA polymerase copies the template strand of DNA.

Answer 2

Correct hydrogen bonding is the primary check of the newly synthesized DNA.

Question 3

An intact 4 kb plasmid has a 50% G+C content,and a 4 kb fragment of E.coli chromosomal DNA has a 55% G+C content.Which of the following is NOT correct when comparing the two?

A)The Tm of the plasmid would be less than the Tm of the chromosomal DNA.
B)The c0t_1/2 value (time required to renature 50% of the DNA molecules)of the plasmid would be more than that of the chromosomal DNA.
C)The plasmid DNA and chromosomal DNA would both show approximately a 30%-40% increase in their absorption at 260 nm upon heating to 90°C.
D)The plasmid DNA would contain more negative supercoiling than the chromosomal DNA fragments.

Answer 3

The c0t_1/2 value (time required to renature 50% of the DNA molecules)of the plasmid would be more than that of the chromosomal DNA.

Question 4

The hyperchromic shift occurs when dsDNA is denatured.At what wavelength is there an increase in the absorption as a result of this shift?

A)200 nm
B)220 nm
C)240 nm
D)260 nm

Question 5

Which of the following stabilizes the DNA double-helix structure?

A)The sugar-phosphate backbones are oriented in parallel directions.
B)Bases stack together through hydrophobic interactions and van der Waals forces.
C)The glycosidic bonds holding paired bases are directly across the helix from one another.
D)Appropriate base pairing builds a polymer whose external dimensions are not consistent.

Question 6

Which of the following is a characteristic of the chain termination protocol?

A)One dNTP is a radioactively labelled tracer to detect the products in the polymerization process.
B)An unknown sequence serves as a template in a polymerization reaction.
C)Two parallel reactions are run,each containing the substrates for DNA polymerase.
D)The chain is terminated where the dideoxynucleotide is incorporated.

Question 7

Which of the following terms is for the naturally occurring,self-replicating,extra-chromosomal DNA molecules found in bacteria that carry genes specifying novel metabolic capacity advantageous to the bacterium?

A)probes
B)cruciform
C)toroidal DNA
D)plasmids

Question 8

Which of the following terms defines the process that occurs when ssDNA reassociates with other ssDNA?

A)diffusion
B)reannealing
C)melting
D)solidifying

Question 9

Sequencing nucleic acids is now easier than sequencing polypeptides.Which of the following developed technologies facilitates this?

A)restriction endonucleases and polyacrylamide gel electrophoresis
B)base-specific chemical cleavage and autoradiography
C)cytosine methylation and base-specific chemical cleavage
D)double-helix denaturation and restriction endonucleases

Question 10

Which of the following is NOT a DNA intercalating agent?

A)ethidium bromide
B)actinomycin D
C)acridine orange
D)streptomycin

Question 11

Which of the following is the function of DNA topoisomerases?

A)packaging DNA into nucleosomes
B)forming cruciform DNA
C)unwinding G:C-rich areas in DNA
D)breaking 1 or more strands of DNA,winding them tighter or looser,and rejoining the ends

Question 12

How is radioactivity incorporated into newly synthesized DNA using the chain termination protocol for sequencing DNA?

A)One of the dNTPs is labelled with ³²P.
B)The primer strand is labelled with ³²P.
C)The 5'-end is labelled with ³²P.
D)The dideoxynucleotide is labelled with ³²P.

Question 13

Which of the following pairs of nucleotides,present in high concentrations,would result in a higher DNA melting temperature?

A)A:T
B)A:U
C)G:C
D)I:G

Question 14

Which of the following is the nucleotide sequence of the DNA strand that is complementary to 5'-ATCGCAACTGTCACTA-3'?

A)5'-TAGCGTTGACAGTGAT-3'
B)5'-UAGUGACAGUUGCGAU-3'
C)5'-ATCACTGTCAACGCTA-3'
D)5'-TAGTGACAGTTGCGAT-3'

Question 15

The UV absorption decrease associated with ssDNAs reannealing can be plotted on a c₀t curve.Which of the following does this graph indicate?

A)that more complex DNAs take longer to renature
B)that more double-stranded RNAs take longer to renature
C)that more simple DNAs take longer to renature
D)that more single-stranded RNAs take longer to renature

Question 16

Which of the following features of DNA is analogous to twisting or untwisting a 2-stranded rope so that it is torsionally stressed?

A)b-sheet
B)hairpin turn
C)cloverleaf
D)supercoiling

Question 17

Which of the following conformations do double-helical DNA:RNA hybrids and double-stranded regions of RNA chains often assume?

A)A-like conformation
B)B-like conformation
C)Z-like conformation
D)triple-helix conformation

Question 18

How do urea and formamide denature dsDNA?

A)by intercalating between base pairs and disrupting van der Waals interactions
B)by forming ionic bonds with the backbone phosphates
C)by competing effectively with the H-bonding between the base pairs
D)by changing the pH to cause hydrolysis

Question 19

Which of the following is a characteristic of DNA polymerase?

A)copies the sequence of nucleotides of one strand in a complementary fashion
B)requires a primer with a free 5'-OH end,but the 3'-end may be phosphorylated
C)copies the sequence of nucleotides of one strand to form two new strands
D)synthesizes new strands by adding successive nucleotides in the 3'?5' direction

Question 20

Nucleic acid hybridization is a common technique used in molecular biology.Which of the following procedures does NOT use this technique?

A)investigation of evolutionary relationships
B)examination of specific genes against a vast background
C)carrying out specific probe-based isolation of proteins
D)quantifying gene expression

Question 21

Which of the following is a characteristic of rRNA strands?

A)interstrand sequence complementarity
B)the absence of modified ribonucleotides
C)an anticodon loop
D)highly folded patterns,including many stem-loop structures

Question 22

Which of the following is NOT a property of nucleosomes?

A)protein spools neatly wrapped with DNA
B)fundamental structural unit in chromatin
C)protein spools made up of single histones H2A,H2B,H3,and H4 octameric aggregates
D)DNA binding of histones by ionic bonds of positively charged amino acids and the negatively charged phosphate groups

Question 23

Which of the following do phylogenetic comparisons of secondary structures of rRNAs from a variety of species reveal?

A)strikingly similar structures and a high degree of similarity in the nucleotide sequences of the rRNAs themselves
B)strikingly similar structures and a low degree of similarity in the nucleotide sequences of the rRNAs themselves
C)dissimilar structures and a high degree of similarity in the nucleotide sequences of the rRNAs themselves
D)dissimilar structures and a low degree of similarity in the nucleotide sequences of the rRNAs themselves

Question 24

How are individual amino acids attached to their corresponding tRNAs?

A)through an ester linkage to the 3'-OH in the acceptor stem
B)through an amide linkage to the anticodon loop
C)through an amide linkage to the adenine ring at the 3'-end of the tRNA
D)through a phosphoester linkage to the 5'-end of the tRNA

Question 25

Which of the following types of structures potentially forms from DNA sequences that are inverted repeats?

A)a secondary structure known as a cruciform
B)a tertiary structure known as a cruciform
C)a secondary structure known as a palindrome
D)a tertiary structure known as a palindrome

Question 26

Which of the following is NOT a secondary structure component of tRNA?

A)acceptor stem
B)b-turn l
C)anticodon loop
D)TYC loop

Question 27

Which of the following is a characteristic of DNA gyrase in E.coli?

A)It hydrolyzes GTP during its reaction mechanism.
B)It cuts only one strand of a dsDNA.
C)It is classified as a topoisomerase.
D)It works to induce positive supercoiling in DNA.

Question 28

Which of the following major interactions assist in folding components of the secondary structure of tRNA together and bending the cloverleaf into a stable L-shaped tertiary form?

A)van der Waals
B)ionic
C)base-pairing
D)electrostatic interactions

Question 29

Which of the following amino acids are rich in histones?

A)alanine and glycine
B)glutamic acid and aspartic acid
C)lysine and arginine
D)lysine and alanine