(1) AP Biology Unit 6 Exam- Gene Expression

In a typical human cell, only about 20% of the genes it contains are expressed (even less in muscle and nerve cells), even though almost all the cells in the organism contain the same DNA. The set of genes expressed in each cell is unique, which allows the cells to perform different functions. This expression of different genes by cells within the same genome is known as:

• Positive gene regulation

• Negative gene regulation

• Differential gene expression

• Genomic imprinting

If a mutation causes a misplacement of a structure on a organisms, such as a leg growing where an antenna on a fruit sly should be, the mutation is most likely to be in:

• Homeotic gene

• ras genes

• p53 genes

• Maternal effect genes

What would be the minimum number of nucleotides required to code for a protein with 12 amino acids?

• 6

• 12

• 36

• 48

Which statement best describes the role of the tryptophan operon when adequate tryptophan is present in the cell?

• The repressor in inactive and the operon is turned “off,” halting the production of tryptophan

• Tryptophan acts as a corepressor and activates the repressor, stopping the production of tryptophan

• The repressor becomes active, the operon is turned “on” and tryptophan is produced

• Tryptophan is present, the repressor is active, and the operon is turned “on”

Mad cow disease causes normal versions of a protein in the brain to misfold, causing brain damage. What is responsible for the change in the shape of the protein?

• Repressor genes

• RNA polymerase

• Prions

• The tryptophan operon

What statement best describes the function of a promoter?

• An enzyme that transcribes a new RNA chain by linking ribonucleotides to nucleotides on a DNA template

• A protein that prohibits gene transcription

• A nucleotide sequence in DNA that is the binding site of RNA polymerase, positioning the RNA polymerase to begin transcription at the appropriate position.

• A sequence of nucleotides near the start of an operon where the active repressor can attach

Energy is required to separate the two strands of the DNA double helix because of the hydrogen bonds between the base pairs. Based on the base pair content, which of the following would require the least amount of energy to separate the strands of DNA?

• 20% G, 20% C, 30% A, 30% T

• 30% G, 30% C, 20% A, 20% T

• 15% A, 15% T, 35% G, 35% C

• 25% A, 25% T, 25% G, 25% C

During this stage of gene expression, mRNA is processed through ribosomes and polypeptides are linked together into chains.

• RNA Processing

• Translation

• Replication

• Transcription

This process involves modifying the ends of the pre-mRNA molecules by modifying each end, cutting out introns, and splicing remaining parts together.

• RNA Processing

• Translation

• Replication

• Transcription

Which shows the correct sequence of information flow from gene to protein?

• Transcription → Translation → RNA processing

• RNA processing → Translation → Transcription

• RNA processing →Transcription  → Translation

• Translation →Transcription  → RNA processing