Question 1

Which of the following experimental results provided the most direct evidence that DNA, and not protein, is the genetic material in bacteriophages?

Accepted Answer

The finding that radioactive phosphorus entered bacterial cells during phage infection, while radioactive sulfur did not

Question 2

Which of the following best explains why regions of DNA with a high proportion of G-C base pairs are more thermally stable than regions rich in A-T base pairs?

Accepted Answer

G-C base pairs are stabilized by three hydrogen bonds, while A-T pairs have only two

Question 3

A scientist isolates a nucleic acid from a cell and determines that it contains ribose sugars and uracil bases. Which type of molecule has the scientist most likely isolated?

Accepted Answer

RNA

Question 4

Which of the following is NOT a criterion that genetic material must fulfill, according to the study materials?

Accepted Answer

It must be capable of self-repair after mutation

Question 5

In the classic experiment by Avery, MacLeod, and McCarty, which treatment prevented the transformation of non-virulent bacteria into virulent bacteria?

Accepted Answer

Treatment with DNase

Question 6

Which of the following statements about the structure of B-form DNA is CORRECT?

Accepted Answer

The diameter of the helix is $$2\ \mathrm{nm}$$

Question 7

A DNA strand has the sequence 5'-ATCG-3'. What is the sequence and polarity of the complementary strand?

Accepted Answer

3'-TAGC-5'

Question 8

Which of the following best describes the difference between a nucleoside and a nucleotide?

Accepted Answer

A nucleoside consists of a base and a sugar, while a nucleotide also includes one or more phosphate groups

Question 9

Which of the following features is unique to Z-DNA compared to B-DNA?

Accepted Answer

It is a left-handed helix with 12 base pairs per turn

Question 10

A researcher finds that a sample of DNA contains 30% adenine. According to Chargaff's rule, what percentage of guanine should be present?

Accepted Answer

$$20\%$$

Question 11

Which of the following best explains why the major groove of DNA is important for protein-DNA interactions?

Accepted Answer

It exposes more of the base edges, allowing proteins to recognize specific sequences

Question 12

Which of the following accurately describes the directionality of a DNA strand?

Accepted Answer

It has a free phosphate group at the 5-prime end and a free hydroxyl group at the 3-prime end

Question 13

Which of the following is a correct pairing of a purine and a pyrimidine found in DNA?

Accepted Answer

Adenine and Thymine

Question 14

Which of the following best describes the secondary structure of tRNA?

Accepted Answer

It forms a cloverleaf pattern with several double-helical regions due to complementary base pairing

Question 15

Which of the following is a real-life application of the concept of transformation as demonstrated by Griffith's experiments?

Accepted Answer

The acquisition of antibiotic resistance genes by pathogenic bacteria from their environment

Question 16

Which of the following best describes the chemical difference between deoxyribose and ribose?

Accepted Answer

Deoxyribose lacks an oxygen atom at the 2-prime carbon compared to ribose

Question 17

Which of the following best explains why Watson and Crick rejected the model in which identical bases pair with each other (A with A, T with T, etc.)?

Accepted Answer

It did not satisfy Chargaff's rule and did not produce a helix with a constant diameter

Question 18

Which of the following is a feature of RNA molecules that allows them to form complex three-dimensional structures?

Accepted Answer

The ability to form short double-stranded regions through complementary base pairing

Question 19

Which of the following best describes a phosphodiester linkage in nucleic acids?

Accepted Answer

A covalent bond connecting the 5-prime phosphate of one nucleotide to the 3-prime hydroxyl of the next

Molecular Structure of DNA and RNA – Study Notes

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