Question 1

Which of the following best describes the conclusion of the Hershey-Chase experiment regarding the genetic material of phages?

Accepted Answer

DNA, not protein, is the genetic material because only DNA entered the bacterial cells and directed viral replication.

Question 2

A DNA molecule has the following sequence on one strand: 5'-ATGCCGTA-3'. What is the complementary sequence on the other strand, and in which direction is it written?

Accepted Answer

3'-TACGGCAT-5'

Question 3

During DNA replication, which enzyme is responsible for synthesizing short RNA primers on the lagging strand?

Accepted Answer

Primase

Question 4

Which of the following statements about euchromatin and heterochromatin is correct?

Accepted Answer

Euchromatin is less condensed and transcriptionally active, while heterochromatin is more condensed and generally inactive.

Question 5

A mutation that inserts a single nucleotide into a coding region of a gene is most likely to cause which of the following?

Accepted Answer

A frameshift mutation

Question 6

Which of the following best explains why a codon must consist of three nucleotides?

Accepted Answer

Because there are only four nucleotides and 20 amino acids, a triplet code ($$4^3 = 64$) provides enough combinations to code for all amino acids.

Question 7

In eukaryotic cells, which of the following modifications occurs to pre-mRNA before it leaves the nucleus?

Accepted Answer

Addition of a 5' cap and a poly-A tail, and removal of introns by splicing

Question 8

Which of the following best describes the function of aminoacyl tRNA synthetase?

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA.

Question 9

The lac operon in E. coli is an example of which type of gene regulation, and under what conditions is it most active?

Accepted Answer

An inducible operon, most active when lactose is present and glucose is low

Question 10

Which of the following statements about DNA methylation is correct?

Accepted Answer

DNA methylation generally decreases gene expression by making DNA less accessible.

Question 11

A scientist uses PCR to amplify a DNA segment. Which of the following is NOT a required component for the reaction?

Accepted Answer

DNA ligase

Question 12

Which of the following best describes the difference between the lytic and lysogenic cycles of a bacteriophage?

Accepted Answer

The lytic cycle results in immediate lysis of the host cell, while the lysogenic cycle allows the phage genome to be replicated with the host genome without killing the cell.

Question 13

A researcher is studying a gene that is present in multiple copies in the human genome, all of which are similar but not identical. What is this group of genes called?

Accepted Answer

A multigene family

Question 14

Which of the following best explains why RNA viruses tend to evolve more rapidly than DNA viruses?

Accepted Answer

RNA viruses have higher mutation rates because their replication enzymes lack proofreading ability.

Question 15

Which of the following is a function of the CRISPR-Cas9 system in biotechnology?

Accepted Answer

It allows for targeted gene editing by creating double-stranded breaks at specific DNA sequences.

Question 16

A patient is diagnosed with Creutzfeldt-Jakob disease, a rare neurodegenerative disorder. This disease is caused by which type of infectious agent?

Accepted Answer

A prion

Question 17

Which of the following best describes a nucleosome?

Accepted Answer

A complex of DNA wrapped around a core of histone proteins

Question 18

Which of the following statements about the human genome is correct?

Accepted Answer

Only about 1.5% of the human genome codes for proteins; the rest includes non-coding regions, regulatory sequences, and repetitive DNA.

Question 19

A scientist is using gel electrophoresis to analyze DNA samples. Which of the following statements is correct regarding how DNA fragments move in the gel?

Accepted Answer

DNA fragments move toward the positive electrode because DNA is negatively charged.

Question 20

Which of the following best describes the function of a proteasome in a eukaryotic cell?

Accepted Answer

It degrades proteins that have been tagged with ubiquitin.

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