MCAT Biochemistry Practice Test 6: DNA and Biotechnology

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1. In a single strand of a nucleic acid, nucleotides are linked by:

  • A. hydrogen bonds.
  • B. phosphodiester bonds.
  • C. ionic bonds.
  • D. van der Waals forces.

2. Which of the following statements regarding differences between DNA and RNA is FALSE?

  • A. DNA is double-stranded, whereas RNA is single-stranded.
  • B. DNA uses the nitrogenous base thymine; RNA uses uracil.
  • C. The sugar in DNA is deoxyribose; the sugar in RNA is ribose.
  • D. DNA strands replicate in a 5′ to 3′ direction, whereas RNA is synthesized in a 3′ to 5′ direction.

3. Which of the following DNA sequences would have the highest melting temperature?


4. Which of the following biomolecules is LEAST likely to contain an aromatic ring?

  • A. Proteins
  • B. Purines
  • C. Carbohydrates
  • D. Pyrimidines

5. For a compound to be aromatic, all of the following must be true EXCEPT:

  • A. the molecule is cyclic.
  • B. the molecule contains 4n + 2 π electrons.
  • C. the molecule contains alternating single and double bonds.
  • D. the molecule is planar.

6. Which of the following enzymes is NOT involved in DNA replication?

  • A. Primase
  • B. DNA ligase
  • C. RNA polymerase
  • D. Telomerase

7. How is cDNA best characterized?

  • A. cDNA results from a DNA transcript with noncoding regions removed.
  • B. cDNA results from the reverse transcription of processed mRNA.
  • C. cDNA is the abbreviation for deoxycytosine.
  • D. cDNA is the circular DNA molecule that forms the bacterial genome.

8. Which of the following statements regarding the polymerase chain reaction is FALSE?

  • A. Human DNA polymerase is used because it is the most accurate.
  • B. A primer must be prepared with a complementary sequence to part of the DNA of interest.
  • C. Repeated heating and cooling cycles allow the enzymes to act specifically and replaces helicase.
  • D. Each cycle of the polymerase chain reaction doubles the amount of DNA of interest.

9. Restriction endonucleases are used for which of the following?

I. Gene therapy

II. Southern blotting

III. DNA repair

  • A. I only
  • B. II only
  • C. II and III only
  • D. I, II, and III

10. How does prokaryotic DNA differ from eukaryotic DNA?

I. Prokaryotic DNA lacks nucleosomes.

II. Eukaryotic DNA has telomeres.

III. Prokaryotic DNA is replicated by a different DNA polymerase.

IV. Eukaryotic DNA is circular when unbound by centromeres.

  • A. I only
  • B. IV only
  • C. II and III only
  • D. I, II, and III only

11. Why might uracil be excluded from DNA but NOT RNA?

  • A. Uracil is much more difficult to synthesize than thymine.
  • B. Uracil binds adenine too strongly for replication.
  • C. Cytosine degradation results in uracil.
  • D. Uracil is used as a DNA synthesis activator.

12. Tumor suppressor genes are most likely to result in cancer through:

  • A. loss of function mutations.
  • B. gain of function mutations.
  • C. overexpression.
  • D. proto-oncogene formation.

13. Which of the following is an ethical concern of gene sequencing?

  • A. Gene sequencing is invasive, thus the potential health risks must be thoroughly explained.
  • B. Gene sequencing impacts relatives, thus privacy concerns may be raised.
  • C. Gene sequencing is very inaccurate, which increases anxiety related to findings.
  • D. Gene sequencing can provide false-negative results, giving a false sense of security.

14. Which of the following is NOT a difference between heterochromatin and euchromatin?

  • A. Euchromatin has areas that can be transcribed, whereas heterochromatin is silent.
  • B. Heterochromatin is tightly packed, whereas euchromatin is less dense.
  • C. Heterochromatin stains darkly, whereas euchromatin stains lightly.
  • D. Heterochromatin is found in the nucleus, whereas euchromatin is in the cytoplasm.

15. During which phase of the cell cycle are DNA repair mechanisms least active?

  • A. G1
  • B. S
  • C. G2
  • D. M