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AP®BiologyCollege BoardExam QuestionsUnit 6: Gene Expression & RegulationDNA, RNA & Protein Synthesis

DNA, RNA & Protein Synthesis (College Board AP® Biology)

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DNA, RNA & Protein Synthesis

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DNA, RNA & Protein Synthesis

1
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The human TP53 gene encodes different forms of tumour suppressor protein. Which of the following best explains how different proteins can be made within different cell types from the one TP53 gene?

  • Different introns are selectively converted to exons.

  • Different exons are retained or spliced out of the primary transcript.

  • The GTP cap is selectively added to and activates different exons.

  • Different portions of the primary transcript remain bound to the template DNA.

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2
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Researchers were investigating the process of transcription in eukaryotic cells. They isolated pre-mRNA molecules from human fibroblast cells and analyzed their lengths using gel electrophoresis. The same mRNA sequences were then isolated from the cytoplasm and analyzed using electrophoresis to separate the sequences by size. The results are shown in Figure 1.

DNA gel electrophoresis image with three lanes; lane 1 has a DNA ladder with sizes marked at 1000, 3500, and 7500 base pairs.

Which of the following conclusions about eukaryotic gene expression is best supported by the data in Figure 1?

  • Transcription occurs more efficiently in the cytoplasm than in the nucleus.

  •  Translation occurs before RNA splicing in eukaryotic cells.

  •  Post-transcriptional modification reduces the length of mRNA molecules.

  •  Eukaryotic genes do not contain introns.

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3
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Scientists are studying the role of a newly identified enzyme in the DNA replication process of eukaryotic cells. They propose that this enzyme is crucial for initiating DNA synthesis by assisting in unwinding the double helix during replication. Which of the following questions would best guide the researchers towards a direct test of their proposal?

  • Does the inhibition of the enzyme prevent the unwinding of DNA at the replication fork?

  • Does the enzyme remain active throughout the G2 phase of the cell cycle?

  • How does the enzyme influence the repair of DNA after replication is completed?

  • Does the enzyme increase the speed of RNA transcription during replication?

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4
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In an experiment to verify the nature of DNA replication, scientists used nitrogen isotopes to label the DNA of E. coli. The bacteria were grown in a medium containing heavy nitrogen (N15) and then switched to a medium containing light nitrogen (N14). The results after one round of replication are shown in the table below.

Round of Replication

% Heavy (N15) DNA

% Hybrid (Mixed N15/N14) DNA

% Light (N14) DNA

0

100

0

0

1

0

100

0

2

0

50

50

Which of the following conclusions is best supported by this data?

  • DNA replication in E. coli is conservative.

  • DNA replication in E. coli is semi-conservative.

  • DNA replication in E. coli results in entirely new DNA after one round of replication.

  • DNA replication does not require nitrogen isotopes.

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5
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Researchers were investigating the role of RNA polymerase in transcription. They set up an in vitro transcription system with purified RNA polymerase, DNA template, and nucleotides. The researchers measured the rate of RNA synthesis under various conditions. The results are shown in Figure 1.

Four graphs of RNA synthesis over time; only the "Complete System" shows a rising curve. The others show flat lines near zero.
Figure 1. RNA synthesis over time in different conditions

Which of the following conclusions about transcription is best supported by the data?

  • RNA polymerase can synthesize RNA without a DNA template.

  • Nucleotides are not necessary for RNA synthesis.

  • RNA polymerase is the primary enzyme responsible for RNA synthesis.

  • Heat does not affect the activity of RNA polymerase.

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