Q: Which equation best represents the semiconservative model of DNA replication after one round?

$$\text{Original DNA} \rightarrow \text{1/2 old strand} + \text{1/2 new strand}$$

Question 1

Which model of DNA replication was supported by the Meselson-Stahl experiment?

Accepted Answer

Semiconservative replication

Question 2

In the Meselson-Stahl experiment, what was the key evidence that supported semiconservative replication?

Accepted Answer

The appearance of hybrid DNA (intermediate density) after one generation

Question 3

Which enzyme is responsible for synthesizing most of the new DNA during E. coli replication?

Accepted Answer

DNA polymerase III

Question 4

What is the primary function of DNA polymerase I in E. coli DNA replication?

Accepted Answer

Excising RNA primers and filling in gaps

Question 5

Which activity allows DNA polymerases to proofread newly synthesized DNA?

Accepted Answer

3'-5' exonuclease activity

Question 6

In E. coli, what is the result of having a single origin of replication on its circular chromosome?

Accepted Answer

Two replication forks are formed and replication is bidirectional

Question 7

Which enzyme relieves the tension created ahead of the replication fork during DNA unwinding?

Accepted Answer

Topoisomerase (e.g., DNA gyrase)

Question 8

What is the role of primase during DNA replication?

Accepted Answer

Synthesizes RNA primers complementary to the DNA template

Question 9

Why is DNA synthesis on the lagging strand discontinuous?

Accepted Answer

Because DNA polymerase can only synthesize in the 5'-3' direction

Question 10

Which enzyme seals the nicks between Okazaki fragments during DNA replication?

Accepted Answer

DNA ligase

Question 11

Eukaryotic chromosomes have multiple origins of replication. What is the term for the DNA replicated from a single origin?

Accepted Answer

Replicon

Question 12

Which of the following is a challenge unique to the replication of linear eukaryotic chromosomes?

Accepted Answer

Replicating the ends of chromosomes (telomeres)

Question 13

What is the function of telomerase in eukaryotic cells?

Accepted Answer

Extends the 3' end of the parental DNA using an RNA template

Question 14

Which equation best represents the semiconservative model of DNA replication after one round?

Accepted Answer

$$	ext{Original DNA} ightarrow 	ext{1/2 old strand} + 	ext{1/2 new strand}$$

Question 15

If a cell undergoes two rounds of semiconservative replication starting with DNA labeled with heavy nitrogen ($$^{15}N$$), what proportion of DNA molecules will be hybrid after the second round?

Accepted Answer

$$1/4$$

Question 16

Which protein complex is responsible for coordinating the activities of multiple enzymes at the replication fork?

Accepted Answer

Replisome

Question 17

During DNA replication, which process ensures that errors are corrected before they become permanent mutations?

Accepted Answer

Proofreading by 3'-5' exonuclease activity

Question 18

In eukaryotic DNA replication, what is the significance of polymerase switching?

Accepted Answer

It allows the transition from RNA primer synthesis to DNA elongation

Question 19

Which of the following best describes homologous recombination?

Accepted Answer

Exchange of genetic material between homologous DNA molecules

Question 20

A mutation in the gene encoding DNA ligase would most directly affect which step of DNA replication?

Accepted Answer

Sealing nicks between Okazaki fragments

DNA Replication and Recombination: Mechanisms and Enzymes

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