Question 1

Which classical experiment first demonstrated that a 'transforming principle' could transfer genetic information between bacteria, and what was the key result?

Accepted Answer

Griffith; showed that heat-killed S strain could transform R strain to cause death in mice

Question 2

In the Hershey & Chase experiment, which isotope was used to label DNA, and what was the significance of its location after infection?

Accepted Answer

$$^{32}P$$; found in bacterial cells, proving DNA is genetic material

Question 3

According to Chargaff’s Rule, if a DNA sample contains 30% adenine, what percentage of guanine would you expect?

Accepted Answer

20%

Question 4

Which scientist’s X-ray crystallography data was critical in determining the double helix structure of DNA?

Accepted Answer

Rosalind Franklin

Question 5

What is the correct pairing of nitrogenous bases in DNA, and how many hydrogen bonds are formed between each pair?

Accepted Answer

A-T: 2 bonds, G-C: 3 bonds

Question 6

Which model of DNA replication was confirmed by the Meselson-Stahl experiment, and what was the key evidence?

Accepted Answer

Semiconservative; one intermediate band after first replication, two bands after second

Question 7

In eukaryotic cells, DNA replication begins at multiple origins. What is the consequence of this for the speed and efficiency of replication?

Accepted Answer

Replication is faster and more efficient because bubbles fuse

Question 8

DNA polymerase III adds nucleotides to which end of the growing DNA strand, and in which direction does it synthesize?

Accepted Answer

Adds to 3' end; synthesizes 5' → 3'

Question 9

What is the function of Okazaki fragments during DNA replication?

Accepted Answer

They are short DNA segments synthesized on the lagging strand

Question 10

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

Accepted Answer

DNA Ligase

Question 11

A mutation occurs in a somatic cell. What is the likely outcome for the organism and its offspring?

Accepted Answer

The mutation will be passed to all daughter cells of the original cell

Question 12

Why are telomeres important for chromosome stability, and what happens to them as cells age?

Accepted Answer

Telomeres buffer coding regions; they shorten with each replication

Question 13

Which enzyme is active in germ cells to rebuild telomeres, and why is this significant for offspring?

Accepted Answer

Telomerase; prevents loss of genetic information in new offspring

Question 14

High levels of telomerase activity are often found in cancer cells. What is the consequence of this?

Accepted Answer

Cancer cells can become 'immortal' and divide indefinitely

Question 15

Chromatin is composed of DNA and proteins. Which proteins are most important for DNA packing, and what is their charge?

Accepted Answer

Histones; positively charged

Question 16

What is the basic unit of chromatin structure, and how is it organized?

Accepted Answer

Nucleosome; DNA wrapped twice around an 8-histone core

Question 17

Which form of chromatin is more accessible for transcription and gene expression?

Accepted Answer

Euchromatin

Question 18

During DNA replication, which enzyme proofreads the newly synthesized DNA and what is the error rate after proofreading?

Accepted Answer

DNA Polymerase; $$1$$ mistake per $$10^{10}$$ nucleotides

Question 19

A cell is exposed to UV radiation, causing DNA damage. Which repair mechanism is most likely to fix this damage, and what are the steps?

Accepted Answer

Nucleotide excision repair; damaged DNA is detected, cut out by nuclease, replaced by polymerase, and sealed by ligase

The Molecular Basis of Inheritance: Structure, Function, and Replication of DNA

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