Question 1

Which of the following is NOT a characteristic of hereditary material as described in modern genetics?

Accepted Answer

It is unable to undergo any mutations, ensuring genetic uniformity.

Question 2

Edmund Wilson’s early suggestion that DNA might be the hereditary material was based on which observation?

Accepted Answer

Sperm and eggs contribute the same number of chromosomes during reproduction.

Question 3

In Frederick Griffith’s experiment with Pneumococcus, what was the key finding that suggested the existence of a 'transformation factor'?

Accepted Answer

Heat-killed S strain bacteria could transform live R strain bacteria into virulent S strain.

Question 4

Which experiment provided direct evidence that DNA is the transformation factor responsible for heredity?

Accepted Answer

Avery, MacLeod, and McCarty’s in vitro transformation experiment.

Question 5

The Hershey-Chase experiment demonstrated that DNA, not protein, is responsible for bacteriophage infection. Which radioactive isotope was used to label DNA?

Accepted Answer

$$^{32}P$$

Question 6

Which of the following correctly describes the antiparallel nature of DNA strands?

Accepted Answer

One strand runs 5' to 3', while the other runs 3' to 5'.

Question 7

Which base pairing rule is correct for DNA?

Accepted Answer

A pairs with T, G pairs with C

Question 8

What is the diameter of B-form DNA across the axis of symmetry?

Accepted Answer

$$20\ 	ext{Å}$$

Question 9

Which form of DNA is most commonly found in cells and has a right-handed helix?

Accepted Answer

B-form

Question 10

The Meselson-Stahl experiment used cesium chloride density gradient centrifugation to distinguish between models of DNA replication. Which model was supported by their results?

Accepted Answer

Semiconservative replication

Question 11

In E. coli, the origin of replication (oriC) contains conserved sequences. What is the consensus sequence for the 13-mer region?

Accepted Answer

TTATCC

Question 12

Which protein in E. coli binds first to the 9-mer sequences at oriC to initiate DNA replication?

Accepted Answer

DnaA

Question 13

During DNA replication, which enzyme synthesizes the RNA primer required for DNA polymerase to begin elongation?

Accepted Answer

Primase

Question 14

Which strand is synthesized discontinuously during DNA replication, resulting in Okazaki fragments?

Accepted Answer

Lagging strand

Question 15

What is the role of DNA ligase during DNA replication?

Accepted Answer

It seals gaps between Okazaki fragments by forming phosphodiester bonds.

Question 16

Which activity allows DNA polymerase to proofread and correct errors during replication?

Accepted Answer

3'-to-5' exonuclease activity

Question 17

Why are telomeres necessary at the ends of linear chromosomes?

Accepted Answer

They prevent loss of essential genetic information during lagging strand replication.

Question 18

Which enzyme is responsible for synthesizing telomeric repeats in germ line cells?

Accepted Answer

Telomerase

Question 19

In the polymerase chain reaction (PCR), what is the purpose of raising the temperature to approximately $$95^\circ	ext{C}$$ during the first step?

Accepted Answer

To denature the double-stranded DNA into single strands.

Question 20

In Sanger sequencing, what is the consequence of incorporating a dideoxynucleotide (ddNTP) into a growing DNA strand?

Accepted Answer

Replication ceases at the point of ddNTP incorporation.

DNA Structure and Replication: Key Concepts in Genetics

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