Question 1

Which experiment first demonstrated that a 'transforming principle' could transfer pathogenicity between bacterial strains, suggesting the existence of genetic material?

Accepted Answer

Griffith's experiment with Streptococcus pneumoniae

Question 2

Avery, MacLeod, and McCarty's experiment built on Griffith's findings. What was their critical contribution to the understanding of genetic material?

Accepted Answer

They demonstrated that DNA, not protein or RNA, is the transforming substance.

Question 3

In the Hershey-Chase experiment, which radioactive isotope was used to label DNA, and what was the key result?

Accepted Answer

Radioactive phosphorus ($$^{32}P$$); it was found inside the bacterial cells

Question 4

Erwin Chargaff discovered that in any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine. Which formula best represents this relationship?

Accepted Answer

$$[A] = [T]$$ and $$[G] = [C]$$

Question 5

Which feature of DNA structure did Rosalind Franklin's X-ray diffraction images help to reveal?

Accepted Answer

The helical nature and regular spacing of the molecule

Question 6

Watson and Crick's model of DNA explained Chargaff's rules by showing that:

Accepted Answer

Adenine pairs with thymine and guanine pairs with cytosine via hydrogen bonds

Question 7

During DNA replication, which enzyme is responsible for unwinding the double helix?

Accepted Answer

Helicase

Question 8

In DNA replication, the leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments. What are these fragments called?

Accepted Answer

Okazaki fragments

Question 9

Which direction does DNA polymerase synthesize new DNA?

Accepted Answer

From the 5' to 3' direction

Question 10

What is the role of single-strand binding proteins during DNA replication?

Accepted Answer

They prevent the separated DNA strands from re-annealing.

Question 11

A mutation occurs during DNA replication. Which process is most likely to correct this error before it becomes permanent?

Accepted Answer

Proofreading by DNA polymerase

Question 12

Which statement best describes the antiparallel nature of DNA?

Accepted Answer

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

Question 13

Chromatin structure changes during the cell cycle. Which form of chromatin is most accessible for gene expression?

Accepted Answer

Euchromatin

Question 14

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

Accepted Answer

DNA can replicate and transmit information with high fidelity.

Question 15

If a DNA sample from a new organism contains 32% adenine, what percentage of guanine would you expect to find?

Accepted Answer

18%

Question 16

Which enzyme relieves the strain caused by unwinding of the DNA double helix during replication?

Accepted Answer

Topoisomerase

Question 17

What is the function of DNA ligase during DNA replication?

Accepted Answer

It joins Okazaki fragments on the lagging strand.

Question 18

Which of the following best describes the structure of a nucleosome?

Accepted Answer

A segment of DNA wrapped around a core of histone proteins

Question 19

Why are mutations important in the context of evolution?

Accepted Answer

They are the source of genetic variation upon which natural selection operates.

Question 20

Which statement about the packing of chromatin in the nucleus is correct?

Accepted Answer

Chromatin is loosely packed during interphase and condenses prior to mitosis.

The Molecular Basis of Inheritance (Chapter 16): Structure, Function, and Replication of DNA

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