Nucleic Acids - Mock Test 3

Question 21

Which of the following forces can stabilize a normal DNA double-helix

A) Base-stacking is a non-covalent interaction that occurs between the relatively hydrophobic bases in the interior of the helix. B) Base-pairing is a non-covalent interaction that occurs between adjacent bases in the same strand of the DNA molecule. C) The hydrophilic sugar-phosphate groups are on the exterior of the helix where they can interact with each other. D) The deoxyribose rings form N-glycosidic bonds with the phosphate groups that link neighboring nucleotides.

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Question 22

When this single strand binds to a complementary DNA strand to form a B-DNA structure

A) half the base-pairs will be A-G pairs and half will be C-T pairs. B) each base will form at least two hydrogen bonds with a base in the opposite stran4⃣ C) the two strands will form an antiparallel left-handed helix with 12 base pairs per turn. D) 3⃣ the two strands will form an antiparallel left-handed helix with 12 base pairs per turn.

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Question 23

Which will be a characteristic of this one single strand

A) The single-stranded chain will contain both ribose and deoxyribose. B) The single-stranded chain will contain both purines and pyrimidines. C) The single-stranded chain will contain one 5’-end and one 3’-en D)

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Question 24

Which characteristic will this double-stranded DNA molecule share with a double-stranded RNA molecule of the same size

A) Both will have secondary structure. B) Both will contain inverted repeats. C) Both will be degraded by base. D) Both will contain four types of base-pairs.

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Question 25

Which of the following double-stranded DNA molecules would denature at a lower temperature than the 40 base-pair double-stranded molecule described above

A) a 40 base-pair molecule in which 25% of the bases are adenines B) a 30 base-pair molecule in which 40% of the bases are guanines C) a 20 base-pair molecule in which 10% of the bases are thymines D) a 10 base-pair molecule in which 20 % of the bases are cytosines

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Question 26

Which force can stabilize a DNA double-helix

A) Hydrophobic bases are found in the interior of the helix where each base pair is stabilized by the same number of hydrogen bonds. B) Hydrophilic sugar-phosphate groups are found on the exterior of the helix where they can interact with water. C) Non-covalent N-glycosidic bonds can form between nitrogenous bases in opposite strands in the helix. D) Covalent base-stacking interactions can occur between adjacent bases within the same strand in the helix.

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Question 27

Which characteristic does this double-stranded molecule have when it forms a B- DNA structure

A) The two strands will have parallel orientation and identical sequences. B) The helix will be right-handed with 12 base-pairs per turn. C) Every base-pair will contain one purine and one pyrimidine. D) There are both covalent and non-covalent bonds between the two chains.

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Question 28

Which structural feature is found in the single-stranded DNA molecule

A) It can have a negatively-charged backbone composed of nitrogenous bases. B) Each 3’,5’-phosphodiester bond will contain one phosphate group linking two deoxyribose sugars. C) It can have one end with a 5’-phosphate group while the other end has a 2’-hydroxyl group. D) Each purine and pyrimidine will be paired with a complementary base.

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Question 29

Which is a general property of both nucleosides and nucleotides

A) Both contain a pentose in the form of a furanose. B) Both contain at least one 5’-phosphate group. C) Both contain a nitrogenous base that forms covalent H-bonds. D) Both contain a hemiacetal or hemiketal bond

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Question 30

Which characteristic is found in both purines and pyrimidines

A) They both have aromatic rings that undergo substantial tautomerization at neutral pH. B) They both are weak bases that can be positively charged at neutral pH. C) They both have multiple pKa values that result in zwitterion forms. D) They both can form stable N-glycosidic bonds with β D-ribofuranose.

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