Unit 3: Nucleic Acids - Practice Quiz

1 Which of the following is a purine base?

2 Which of the following is a pyrimidine base?

3 How many rings are present in a purine base?

4 Which pyrimidine base is found in RNA but not normally in DNA?

5 A nucleoside consists of a nitrogenous base attached to which molecule?

6 What additional component distinguishes a nucleotide from a nucleoside?

7 Which sugar is present in DNA nucleotides?

8 Which sugar is present in RNA nucleotides?

9 What is the main cellular role of ATP?

10 What does ATP stand for?

11 Which nucleotide is commonly known as the cellular energy currency?

12 Which nucleotide commonly acts as a second messenger in cells?

13 What is the usual shape of a DNA molecule?

14 Which base pairs with adenine in DNA?

15 Which type of bond joins complementary bases in DNA?

16 How many strands does most cellular RNA contain?

17 Which base replaces thymine in RNA?

18 Which type of RNA carries amino acids to the ribosome?

19 Why are nucleic acids generally negatively charged at physiological pH?

20 What happens to DNA strands during denaturation?

21 Which structural feature distinguishes purines from pyrimidines?

22 Which base would be expected to pair with cytosine in a normal DNA double helix?

23 A mutation replaces a thymine base with uracil in a DNA molecule. Which statement best describes the change?

24 Which combination correctly describes a nucleotide?

25 A molecule contains adenine linked to ribose but no phosphate group. What is it called?

26 What type of bond connects the nitrogenous base to the pentose sugar in a nucleoside?

27 In a DNA nucleotide, where is the phosphate group commonly attached when the nucleotide is incorporated into a strand?

28 Why is ATP considered an important cellular nucleotide?

29 Which nucleotide functions as a major intracellular second messenger in many hormone-signaling pathways?

30 NAD is biologically important primarily because it can:

31 Which nucleotide derivative is most directly involved in activating glucose for glycogen synthesis?

32 Two DNA strands are described as antiparallel. What does this mean?

33 A DNA sample contains adenine. Assuming standard base pairing, what percentage of the sample is guanine?

34 Why does a DNA molecule with a higher proportion of G–C base pairs generally require more heat to separate its strands?

35 Which feature of DNA allows one strand to serve as a template for accurate synthesis of the other?

36 Which chemical feature makes RNA more susceptible than DNA to alkaline hydrolysis?

37 Which base is present in RNA in place of thymine?

38 A single RNA strand folds into a hairpin structure. Which interaction most directly stabilizes this structure?

39 Why do nucleic acids migrate toward the positive electrode during electrophoresis?

40 When double-stranded DNA is heated, its absorbance at approximately increases. What is this effect called?

41 Which statement best explains why purine biosynthesis is generally more metabolically expensive than pyrimidine biosynthesis?

42 A base-pairing mutation replaces a cytosine with a base that retains one ring but has a carbonyl pattern resembling thymine. Which classification is most appropriate for the replacement base?

43 Which structural change converts adenosine into AMP without changing the identity of its nitrogenous base?

44 Why is the bond connecting a purine to its sugar described as an N-glycosidic bond rather than an O-glycosidic bond?

45 A nucleotide contains 2′-deoxyribose and a uracil base. Which description is chemically correct?

46 Which feature of ATP most directly enables it to act as a phosphoryl-group donor in many biochemical reactions?

47 A cell has abundant ATP but a very low ATP-to-ADP ratio. Which interpretation is most accurate?

48 Why does cyclic AMP function primarily as a signaling molecule rather than as a direct building block of nucleic acid polymers?

49 Which nucleotide derivative is most directly involved in activating sugars for glycogen or glycoprotein biosynthesis?

50 A double-stranded DNA molecule contains 18% guanine. What percentage of its bases is thymine?

51 A DNA duplex has one strand with the sequence 5′-AGTC-3′. Which is the correct complementary strand orientation and sequence?

52 Why does a DNA molecule with a higher fraction of GC base pairs generally require a higher temperature to denature under comparable conditions?

53 A DNA sample is treated with a reagent that cleaves phosphodiester bonds but leaves bases intact. Which structural feature is directly disrupted?

54 Which property most directly explains why RNA is generally more susceptible than DNA to alkaline hydrolysis?

55 A mutation changes a stable RNA hairpin into a sequence unable to form complementary stem pairs. Which structural level is most immediately affected?

56 Why can an RNA molecule form more diverse catalytic structures than a typical single-stranded DNA molecule?

57 During spectrophotometric analysis, nucleic acid absorbance is measured near 260 nm. What primarily causes this absorbance?

58 When double-stranded DNA is heated, its absorbance at 260 nm increases. This phenomenon is called hyperchromicity and primarily reflects:

59 Why does increasing ionic strength generally reduce the melting temperature of neither DNA nor RNA; instead, it commonly increases duplex stability?

60 A DNA preparation has an absorbance ratio substantially below the value expected for pure DNA. Which contaminant most plausibly explains this result?