Question 1

Which type of chemical bond links nucleotides together in a single strand of DNA?

Accepted Answer

Phosphodiester bonds

Question 2

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

Accepted Answer

The strands are antiparallel, one runs 5’ to 3’ and the other 3’ to 5’

Question 3

Which nitrogenous base pairs with cytosine in a DNA molecule?

Accepted Answer

Guanine

Question 4

If one strand of DNA has the sequence 5’-ACGTT-3’, what is the sequence of the complementary strand?

Accepted Answer

3’-TGCAA-5’

Question 5

During DNA replication, in which direction are new DNA strands synthesized?

Accepted Answer

5’ to 3’

Question 6

Which experiment provided the first direct experimental proof that DNA is the biomolecule responsible for heredity?

Accepted Answer

Avery, MacLeod, and McCarty’s experiment

Question 7

Why was phosphorus-32 ($$^{32}P) $$used to label DNA and sulfur-35 ($$^{35}S) $$used to label protein in the Hershey-Chase experiment?

Accepted Answer

Because $$^{32}P$$ labels DNA (phosphate backbone) and $$^{35}S$$ labels protein (cysteine/methionine)

Question 8

What is the periodicity observed in X-ray diffraction studies of DNA, and what does it indicate about DNA structure?

Accepted Answer

$$3.4$$ angstroms, indicating a helical structure

Question 9

Which of the following is NOT a nitrogenous base found in DNA?

Accepted Answer

Uracil

Question 10

Which of the following best explains why DNA, and not protein, is the genetic material in most organisms?

Accepted Answer

DNA content correlates with chromosome sets in gametes and diploids, but protein content does not

Question 11

Which scientist’s work provided the first evidence that a 'transforming principle' could transfer genetic information between bacteria?

Accepted Answer

Frederick Griffith

Question 12

What is the main function of the sugar-phosphate backbone in the DNA double helix?

Accepted Answer

To provide structural stability and polarity

Question 13

Which of the following is a direct application of recombinant DNA technology in medicine?

Accepted Answer

Production of human insulin in bacteria

Question 14

A transgenic mouse expresses a human gene and passes it to its offspring. What does this demonstrate?

Accepted Answer

That DNA can be inherited and expressed across species

Question 15

Which of the following statements about Chargaff’s rules is correct?

Accepted Answer

The amount of adenine equals the amount of thymine in DNA

Question 16

Which of the following best describes the chemical structure of the sugar in DNA?

Accepted Answer

Deoxyribose, a five-carbon sugar lacking a hydroxyl group at the 2’ position

Question 17

Which of the following is a real-world consequence if carbon-14 ($$^{14}C) $$was used to label both DNA and protein in the Hershey-Chase experiment?

Accepted Answer

It would not distinguish between DNA and protein, making results inconclusive

Question 18

Which of the following is an example of indirect evidence that DNA is the genetic material?

Accepted Answer

The correlation between DNA content and chromosome sets in gametes and diploids

Question 19

Which of the following best explains why mitochondria and chloroplasts are considered to have their own genetic material?

Accepted Answer

They contain DNA that is distinct from nuclear DNA

Question 20

Which of the following is a correct statement about the Human Genome Project?

Accepted Answer

It mapped and sequenced the entire human genome, advancing molecular biology

DNA Structure and Analysis: Evidence for DNA as Genetic Material

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