Question 1

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

Accepted Answer

Hershey and Chase's experiment using T2 bacteriophage and radioactive isotopes

Question 2

According to Chargaff’s rules, if a DNA sample contains 30% adenine, what percentage of guanine would you expect to find?

Accepted Answer

$$20\%$$

Question 3

Which of the following best describes the structure of a DNA double helix?

Accepted Answer

Two antiparallel strands held together by hydrogen bonds between complementary bases

Question 4

What is the function of DNA ligase during DNA replication?

Accepted Answer

Joins Okazaki fragments on the lagging strand

Question 5

Which enzyme relieves the strain caused by the unwinding of the DNA double helix during replication?

Accepted Answer

Topoisomerase

Question 6

A mutation occurs that disables the proofreading function of DNA polymerase. What is the most likely consequence?

Accepted Answer

Increased frequency of mutations in the daughter DNA

Question 7

Which of the following statements about the semiconservative model of DNA replication is correct?

Accepted Answer

Each daughter DNA molecule consists of one parental strand and one new strand

Question 8

During DNA replication, which direction does DNA polymerase synthesize the new DNA strand?

Accepted Answer

5' to 3' direction

Question 9

Which of the following best explains why Okazaki fragments are formed during DNA replication?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end, so the lagging strand is synthesized discontinuously

Question 10

A scientist is studying a eukaryotic cell and observes multiple replication bubbles along a DNA molecule. What does this indicate about DNA replication in eukaryotes?

Accepted Answer

Replication begins at multiple origins and proceeds bidirectionally

Question 11

Which of the following is NOT a component of a DNA nucleotide?

Accepted Answer

A ribose sugar

Question 12

In the classic experiment by Frederick Griffith, what was the key finding when heat-killed S cells were mixed with living R cells and injected into mice?

Accepted Answer

The mice died, and living S cells were recovered from them

Question 13

Which of the following best describes the role of histones in eukaryotic cells?

Accepted Answer

They package and organize DNA into chromatin

Question 14

A patient has a genetic disorder caused by a single base substitution in a gene. Which DNA repair mechanism is most likely to correct this type of error?

Accepted Answer

Mismatch repair

Question 15

Which of the following statements about mutations is correct?

Accepted Answer

Mutations are the source of genetic variation and can be beneficial, neutral, or harmful

Question 16

Which of the following is a correct pairing of nitrogenous bases in DNA?

Accepted Answer

Adenine with thymine

Question 17

If a DNA molecule is 2 nm in diameter and makes a full turn every 10 base pairs, what is the length of one full turn of the helix?

Accepted Answer

$$3.4\ nm$$

Question 18

Which of the following best explains why DNA replication is described as 'antiparallel'?

Accepted Answer

The two DNA strands run in opposite directions, with one strand oriented 5' to 3' and the other 3' to 5'

Question 19

A researcher finds a bacterial cell with a mutation that prevents the synthesis of single-strand binding proteins. What is the most likely effect on DNA replication?

Accepted Answer

Single-stranded DNA will re-anneal or form secondary structures, inhibiting replication

Question 20

Which of the following is a direct consequence of the semiconservative model of DNA replication, as demonstrated by the Meselson-Stahl experiment?

Accepted Answer

After one round of replication in $$^{14}N$$ medium, all DNA molecules have intermediate density

Ch 16. The Molecular Basis of Inheritance: DNA Structure, Replication, and Chromosome Organization

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