Practice Exam On Biochemistry: Quiz!

1. The unwinding of DNA is an energetically favorable process to allow replication.

True

False

2. In E. coli, the replication fork copies DNA continuously and segmented in a 360^o direction.

True

False

3. Stacked base pairs absorb less light in native DNA.

True

False

4. In E.coli, only one replication fork is needed to replicate a new DNA strand.

True

False

5. The component(s) of DNA which is responsible for the absorbance band at 250-270 nm is:

Bases, pentoses, and phosphates all contribute

Only bases

Only bases and pentoses

Only pentoses and phosphates

6. The oligonucleotide, AUGGp, has all these properties except:

Composed of ribonucleotides

Contains a 3' phosphate

Composed of deoxyribonucleotides

Contains three phosphodiester bonds

7. Eukaryotic DNA can contain more than 2 replication forks.

True

False

8. The rate of DNA renaturation is an index of its homology.

True

False

9. The separation of a double-stranded DNA will form two template strands.

True

False

10. RNA can form an unstable hybrid structure with DNA.

True

False

11. The Klenow fragment of E. coli DNA polymerase I can be used to add nucleotides to a DNA with staggered ends if the ends

Are recessed with 5'-phosphates

Are recessed with 3'-OHs

Are extended with 5'-phosphates

Are extended with 3'-OHs

12. Due to nitrogenous bases, UV abs. of DNA increases when heated above body temperature.

True

False

13. DNA is unwound by gyrase without breaking it.

True

False

14. The shorter the primer, the more specific the DNA.

True

False

15. Z-DNA can be stable in A:T-rich regions allowing its transition from B-DNA form.

True

False

16. DNA replication mainly occurs in a conservative manner.

True

False

17. Template strands are only copied continuously.

True

False

18. Which of the following is not a characteristic for DNA synthesis?

DNA polymerase adds nucleotides in a 5'--> 3' direction

A primer strand of DNA must contain a free 3'-OH end

The primer strand of DNA determines which nucleotides are added next

The correct complementary hydrogen bonding between base pairs is the primary check on the fidelity of the newly synthesized DNA

19. The linking number of a highly supercoiled plasmid can be readily changed without producing a relaxed DNA by

Changing the temperature

Increasing salt concentration

The action of topoisomerase

The action of a nuclease such as pancreatic DNase

20. Replication occurs mainly during the G2 and G1 phases where cell growth occurs.

True

False

21. The polymerase which plays a similar role as that of Prokaryotic polII in eukaryotic replication is?

DNA polymerase alpha

DNA polymerase delta

DNA polymerase gamma

DNA polymerase kappa

22. Which is not a property of E. coli DNA polymerase III?

It is responsible for incorporating most of the nucleotides in the lagging strand.

It synthesizes most of the leading strand prior to aiding in the synthesis of the lagging strand.

It contains a 3¨ to 5¨ exonuclease activity.

It synthesizes the leading strand and the lagging strand at the same time

Submit

24. Which E. coli enzyme has the greatest frequency of incorporating the incorrect nucleotide into its nucleic acid polymer?

RNA polymerase

DNA polymerase I

DNA polymerase III

Klenow fragment from DNA polymerase I

25. An individual heterogeneous nuclear RNA (hnRNA)

Contains intron sequences not found in the final mature mRNA.

Contains exon sequences which are removed prior to translation.

Encodes more than one protein.

Can be found in the cytoplasm.

26. What statement is incorrect about the different RNA molecules?

TRNAs contain numerous intramolecular hydrogen bonds between bases.

There are more distinct tRNA molecules than there are rRNA molecules.

RRNAs are complexed to proteins in the ribosome.

The most abundant RNA molecule in the cell is mRNA.

27. E. coli replication on the lagging strand

Is primarily carried out by DNA polymerase I

Is synthesized continuously

This DNA strand is synthesized in a 3'-5'direction of synthesis

Is initially synthesized as Okazaki fragments

28. Which of the following double-stranded DNAs may convert to a cruciform structure?

ATGCATGCATGCATGC/ TACGTACGTACGTACG

CATTAAGCAGTGCTTAAGA/ GTAATTCGTCACGAATTCT

ATATATATGCGCGCGCGC/ TATATATACGCGCGCGCG

AAAAAAAAACCCCCCCCC/ TTTTTTTTTGGGGGGGG

29. Which statement is incorrect about the structure of native E. coli chromosomal DNA?

The DNA is primarily in the B-helix.

The DNA is circular and supercoiled

The DNA exists as a right-handed double helix.

The DNA is one large linear piece about 4000 kb in length.

Submit

38. Reverse transcriptase

Can be a telomerase that uses its own RNA as template.

Is contained in all RNA tumor viruses.

Allows the transcription of cDNA from an RNA template to form a DNA:RNA hybrid.

Can be inhibited by HIV therapy.

All of the above

39. Which one of the following characteristics is not associated with E. coli primase?

It synthesizes the RNA primer in DNA replication.

It is a specific RNA polymerase.

It is essential for DNA replication.

It is also a gyrase

40. DNA-dependent RNA polymerase acts on the DNA template in eukaryotic cells in the synthesis of

A 5'-3' hnRNA transcript as the RNA polymerase moves in the 3'-5' direction on the DNA template

A mature RNA transcript as the RNA polymerase moves in the 5'-3' direction

An RNA transcript, with the sigma subunit of polymerase dissociating after the initiation event

41. The RNA molecules which are involved in processing the hnRNA are:

MRNA

TRNA

RRNA

SnRNA

42. A DNA is found to exhibit a melting temperature of 75 C in 0.1 M NaCl. Under what experimental conditions would the Tm be increased?

Decreasing the concentration of DNA.

Increasing the concentration of NaCl in the solution.

Adding 1% urea (an organic denaturant).

All of the above.

43. A feature which is distinctive to Z-DNA is

A left-handed helix

It has 12 bases per turn

It is found in vivo

All of the above

44. E. coli DNA polymerase I has all the following characteristics except

A 5'-3' exonuclease activity on a second subunit in the polymerase

A 3'-5' exonuclease activity

A 5'-3' DNA polymerase activity

Modest processivity (ca. 20 nucleotides)

45. In the repair of DNA, the E. coli DNA polymerase involved performs which function in addition to its polymerase activity?

It recognizes the abnormality in the duplex DNA structure.

It nicks the DNA to provide a 3'-OH.

It removes the damaged section of DNA with its 5'-3' exonuclease activity.

It ligates the DNA after the repair synthesis.

46. Which of the following is not a characteristic of replication of the E. coli circular chromosome?

Replication is bidirectional.

It initiates at a unique position called oriC.

Torsional stress introduced in the duplex DNA is relieved by DNA gyrase.

The unwinding of the duplex DNA is driven by the translocation of the DNA polymerase.

47. Which statement is incorrect about E. coli DNA polymerase I?

The cell contains more molecules of DNA pol I than DNA pol III.

DNA pol I is a single polypeptide with three domains.

DNA pol I is involved in the repair of UV damaged DNA.

DNA pol I has a larger turnover number than DNA pol III.

Submit

50. Which of the following is not true about tRNA and rRNA?

TRNA can self-base pair forming loops and base pair with non-canonical bases

TRNA can carry at least one amino acid and contain an anticodon.

RRNA is used for ribosome assembly as large and small units that are exported to the cytosol.

RRNA can self-base pair with its complementary strand in a double stranded structure.

Ribosomes contain rRNA as well as proteins except that the former is greater in number.

51. Which of the following statements is not true?

Replication occurs during the S phase of the eukaryotic cell cycle.

Helicase is an ATP-dependant protein that unwinds DNA during replication.

DNA Pol I uses its 3’--> 5’ exonuclease activity to remove primers.

Ligase seals nicks in DNA by covalently linking Okazaki fragments.

DNA Pol I has two types of exonuclease activities.

52. Which of the following is true of replication?

It creates a complementary strand relying upon base-stacking interactions.

Usually, one replication fork must move 360o around the entire chromosome in E.coli.

DNA Pol I adds a new nucleotide to the 5’-end of an existing DNA molecule.

DNA Pol I adds a new nucleotide to the 3’-end of the template strand.

An antiparallel DNA strand is produced and a pyrophosphate is released.

53. Which of the following statements is true about chromosomes?

They must be packed around the cell membrane.

They can exist as unwrapped DNA.

Genetic information is not located in these structures.

As part of their structure, chromatin contains histones wrapped by DNA.

None of the above.

54. DNA Pol III

Synthesizes Okazaki fragments.

Functions mainly in DNA repair.

Polymerizes DNA in a 5’--> 3’ direction

A and c are correct.

None of the above.

55. Under which of the following conditions does the melting temp. for DNA denaturation increase?

Smaller DNA fragments

Higher G-C contents in DNA

Higher A-T contents in DNA

A and c are correct

None are correct

56. Part 1. Determine W, T and L respectively if DNA gyrase puts 4 negative supercoils into the 200-bp circular DNA.

W

T

L

Submit

57.

1

2

3

4

5

6

7

Submit