Question 1

Which experiment provided the first evidence that DNA, not protein, is the genetic material responsible for inheritance?

Accepted Answer

Hershey-Chase experiment

Question 2

A scientist extracts DNA from a new species and finds that 30% of the bases are adenine (A). According to Chargaff's rules, what percentage of the bases should be cytosine (C)?

Accepted Answer

$$20\%$$

Question 3

Which structural feature of DNA was revealed by Rosalind Franklin's Photo 51?

Accepted Answer

DNA is a double helix with a regular repeating structure

Question 4

The Meselson-Stahl experiment used isotopes of nitrogen to demonstrate which model of DNA replication?

Accepted Answer

Semiconservative

Question 5

Why is the lagging strand synthesized in short segments called Okazaki fragments during DNA replication?

Accepted Answer

Because DNA polymerase can only synthesize DNA in the $$5' \rightarrow 3'$$ direction, and the lagging strand must be built in the opposite direction from how the fork opens

Question 6

Which enzyme is responsible for unwinding the DNA double helix at the replication fork?

Accepted Answer

Helicase

Question 7

A mutation changes a codon from $$GAA ($$glutamic acid) to $$GAG ($$also glutamic acid). What type of mutation is this?

Accepted Answer

Silent

Question 8

What is the main consequence of a thymine dimer caused by UV light?

Accepted Answer

It distorts the DNA backbone, which can block or cause errors in DNA polymerase reading through that region

Question 9

Which enzyme removes RNA primers and replaces them with DNA nucleotides during DNA replication?

Accepted Answer

DNA polymerase I

Question 10

What is the function of telomeres, and why do they shorten with each cell division?

Accepted Answer

Telomeres are repetitive noncoding DNA that protect chromosome ends; they shorten with each division because most cells lack telomerase to fully regenerate them

Question 11

Which type of chromatin is loosely packed and actively involved in gene transcription?

Accepted Answer

Euchromatin

Question 12

A point mutation occurs during DNA replication, but is corrected before the next round of replication. Which DNA repair mechanism is most likely responsible?

Accepted Answer

Mismatch repair

Question 13

Which of the following best describes the role of DNA ligase during DNA replication?

Accepted Answer

Seals the gaps between Okazaki fragments on the lagging strand

Question 14

If a cell is exposed to UV light and develops a thymine dimer, which repair mechanism is most likely to fix this damage?

Accepted Answer

Nucleotide excision repair

Question 15

Which of the following statements about the directionality of DNA synthesis is correct?

Accepted Answer

DNA is synthesized in the $$5' \rightarrow 3'$$ direction

Question 16

A bacteriophage injects its genetic material into a bacterial cell. Which molecule enters the cell and directs the production of new viruses?

Accepted Answer

DNA

Question 17

Which of the following best explains why eukaryotic chromosomes have multiple origins of replication?

Accepted Answer

Eukaryotic chromosomes are linear and much larger, so multiple origins ensure the entire genome is replicated efficiently

Question 18

Which of the following is a direct result of a non-conservative missense mutation?

Accepted Answer

A new amino acid with different properties is incorporated, potentially altering protein function

Question 19

Which process is responsible for the compaction of DNA into the microscopic nucleus of a eukaryotic cell?

Accepted Answer

Chromosome packaging with histone proteins

Question 20

Which of the following best describes the antiparallel nature of DNA?

Accepted Answer

One strand runs $$5' \rightarrow 3'$$, and the other runs $$3' \rightarrow 5'$$

The Molecular Basis of Inheritance: Structure, Replication, and Repair of DNA

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