Q: Erwin Chargaff discovered that in any species, the amount of adenine ($$A) is $$equal to the amount of thymine ($$T$$), and the amount of guanine ($$G) is $$equal to the amount of cytosine ($$C). $$Which equation best represents this relationship?

$$A = T$$ \,\text{and}\, G = C$

Question 1

Which experiment provided the first evidence that DNA, and not protein, is the genetic material responsible for heredity in bacteria?

Accepted Answer

Oswald Avery, Maclyn McCarty, and Colin MacLeod's experiment with purified DNA

Question 2

Alfred Hershey and Martha Chase used radioactive isotopes in their experiments with bacteriophages. What was the main conclusion from their work?

Accepted Answer

DNA is the genetic material because only DNA entered the bacterial cell and directed viral replication

Question 3

Erwin Chargaff discovered that in any species, the amount of adenine ($$A) is $$equal to the amount of thymine ($$T$$), and the amount of guanine ($$G) is $$equal to the amount of cytosine ($$C). $$Which equation best represents this relationship?

Accepted Answer

$$A = T$$ \,	ext{and}\, G = C$

Question 4

Rosalind Franklin's X-ray diffraction images of DNA were critical in helping Watson and Crick deduce the structure of DNA. What key feature did her images reveal?

Accepted Answer

The double helix structure with a consistent diameter

Question 5

Which statement best describes the semiconservative model of DNA replication, as demonstrated by Meselson and Stahl?

Accepted Answer

Each new DNA molecule consists of one old strand and one new strand

Question 6

During DNA replication, why is the synthesis of the lagging strand discontinuous?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end, and the lagging strand runs in the opposite direction

Question 7

What is the role of Okazaki fragments in DNA replication?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand, later joined by DNA ligase

Question 8

Which enzyme is responsible for joining Okazaki fragments together during DNA replication?

Accepted Answer

DNA ligase

Question 9

A DNA molecule is described as 'antiparallel.' What does this mean?

Accepted Answer

One strand runs 5' to 3', and the other runs 3' to 5'

Question 10

Which of the following best describes the function of helicase during DNA replication?

Accepted Answer

It unwinds the DNA double helix at the replication fork

Question 11

In a scenario where a mutation affects the function of single-stranded binding proteins (SSBPs), what would likely happen during DNA replication?

Accepted Answer

The DNA strands would re-anneal, preventing proper replication

Question 12

Topoisomerase is essential during DNA replication. What is its primary function?

Accepted Answer

It relieves strain by cutting, swiveling, and rejoining DNA ahead of the replication fork

Question 13

Which of the following is NOT a function of DNA polymerase during replication?

Accepted Answer

Joining Okazaki fragments together

Question 14

A nucleosome is the basic unit of DNA packaging in eukaryotic cells. Which statement best describes its structure?

Accepted Answer

A nucleosome consists of DNA wrapped around a core of eight histone proteins

Question 15

Chromatin is composed of DNA and proteins. Which of the following best describes its function in the cell?

Accepted Answer

Chromatin packages DNA into a compact, organized structure, allowing for efficient regulation of gene expression

Question 16

If a DNA molecule has 30% adenine ($$A$$), what percentage of guanine ($$G) $$would you expect, according to Chargaff's rules?

Accepted Answer

20%

Question 17

During DNA replication, the origin of replication is important because:

Accepted Answer

It is the site where the double helix is first unwound and replication begins

Question 18

A patient has a genetic disorder caused by a defect in DNA ligase. Which process would be most directly affected?

Accepted Answer

Joining of Okazaki fragments on the lagging strand

Question 19

Which of the following best explains why continuous synthesis of both DNA strands is not possible during replication?

Accepted Answer

The two strands of DNA are antiparallel, and DNA polymerase can only add nucleotides to the 3' end

Question 20

Which of the following best describes the role of a primer in DNA replication?

Accepted Answer

A primer is a short RNA sequence that provides a starting point for DNA polymerase

Chapter 16: The Molecular Basis of Inheritance – Study Notes

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