Question 1

Which experimental evidence was most critical in demonstrating that DNA, and not protein, is the genetic material in cells?

Accepted Answer

The ability of heat-killed pathogenic bacteria to transform non-pathogenic bacteria, and the loss of this ability when DNA was destroyed.

Question 2

Which of the following best describes the structure of a DNA molecule?

Accepted Answer

Two antiparallel polynucleotide strands twisted into a double helix.

Question 3

If a segment of DNA has the sequence $5'	ext{-}ATCGGTA\ 3'$ on one strand, what is the sequence of the complementary strand (with correct polarity)?

Accepted Answer

$3'	ext{-}TAGCCAT\ 5'$

Question 4

Which of the following statements about the 5' and 3' ends of DNA is correct?

Accepted Answer

The 5' end has a free phosphate group, and the 3' end has a free hydroxyl group.

Question 5

According to Chargaff's rules, if a DNA sample contains 28% adenine, what percentage of guanine does it contain?

Accepted Answer

22%

Question 6

Which feature of DNA structure allows it to serve as a template for its own replication?

Accepted Answer

Complementary base pairing between the two strands.

Question 7

During DNA synthesis, which enzyme is primarily responsible for adding new nucleotides to the growing DNA strand?

Accepted Answer

DNA polymerase

Question 8

A scientist isolates a DNA molecule and finds it contains 32% cytosine. What is the percentage of thymine in this DNA?

Accepted Answer

18%

Question 9

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

Accepted Answer

The two strands run in opposite 5' to 3' directions.

Question 10

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

Accepted Answer

A ribose sugar

Question 11

A mutation changes a cytosine (C) to a thymine (T) in one strand of DNA. What is the most likely effect on the complementary strand after DNA replication?

Accepted Answer

A guanine (G) will be replaced by an adenine (A) on the complementary strand.

Question 12

Which of the following best describes the backbone of a DNA molecule?

Accepted Answer

Alternating sugar and phosphate groups linked by covalent bonds.

Question 13

If a DNA molecule is 1 megabase (Mb) in length, how many base pairs does it contain?

Accepted Answer

$1,000,000$ base pairs

Question 14

Which of the following real-world scenarios best illustrates the concept of transformation in bacteria?

Accepted Answer

A harmless strain of bacteria becomes deadly after exposure to DNA from a heat-killed pathogenic strain.

Question 15

Which of the following is a correct representation of complementary base pairing in DNA?

Accepted Answer

$A$ pairs with $T$ and $G$ pairs with $C$

Question 16

Which historical discovery provided direct evidence for the helical structure of DNA?

Accepted Answer

X-ray diffraction experiments by Rosalind Franklin

Question 17

Which of the following best explains why DNA can store genetic information for all living organisms despite having only four types of nucleotides?

Accepted Answer

The sequence of nucleotides can be arranged in countless combinations, encoding vast amounts of information.

Question 18

During DNA replication, what is the result of the process described as 'semiconservative'?

Accepted Answer

Each new DNA molecule consists of one old strand and one newly synthesized strand.

Question 19

Which of the following best describes the polarity of the two strands in a DNA double helix?

Accepted Answer

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

Question 20

A DNA molecule is found to have 18% thymine. What is the percentage of cytosine in this molecule?

Accepted Answer

32%

DNA Structure and Function: Study Notes for General Chemistry

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