Question 1

Which experiment provided the first evidence that DNA could transform bacteria, and what was the key result?

Accepted Answer

Griffith experiment; showed that heat-killed pathogenic bacteria could transfer their traits to living nonpathogenic bacteria.

Question 2

In the Griffith experiment, which combination of bacterial strains resulted in the death of the mouse and the recovery of living S cells?

Accepted Answer

Mixture of heat-killed S cells and living R cells

Question 3

What is the definition of 'transformation' as demonstrated in Griffith's experiment?

Accepted Answer

A change in genotype and phenotype due to assimilation of external DNA by a cell

Question 4

In the Hershey-Chase experiment, which molecule was found inside the bacterial cells after infection by phages?

Accepted Answer

Radioactive DNA

Question 5

Why did Hershey and Chase use radioactive sulfur and phosphorus in their experiment?

Accepted Answer

To distinguish between protein and DNA in phages

Question 6

What conclusion did Hershey and Chase reach regarding the genetic material of phages?

Accepted Answer

DNA is the genetic material

Question 7

According to Chargaff’s rules, if a DNA sample contains 32% adenine, what percentage of thymine would you expect?

Accepted Answer

32%

Question 8

Given the following base percentages in wheat DNA: Adenine 28.1%, Guanine 21.8%, what is the expected percentage of cytosine?

Accepted Answer

22.7%

Question 9

Which structural feature of DNA did Watson and Crick’s model explain using X-ray diffraction data?

Accepted Answer

The double helix with antiparallel sugar-phosphate backbones

Question 10

What is the chemical difference between the sugars in DNA and RNA?

Accepted Answer

DNA contains deoxyribose; RNA contains ribose

Question 11

Which base pairing is consistent with the width of the DNA double helix as revealed by X-ray diffraction?

Accepted Answer

Purine + pyrimidine

Question 12

How many hydrogen bonds are formed between guanine and cytosine in DNA?

Accepted Answer

Three

Question 13

If a DNA strand has the sequence 5'-GAATTC-3', what is the complementary strand?

Accepted Answer

3'-CTTAAG-5'

Question 14

Which scientist’s X-ray diffraction photograph was critical in determining the helical structure of DNA?

Accepted Answer

Rosalind Franklin

Question 15

What is the directionality of a DNA strand?

Accepted Answer

It runs from the 5' end to the 3' end

Question 16

Which equation represents the relationship between the base pairs in double-stranded DNA according to Chargaff’s rules?

Accepted Answer

$$A = T$$ and $$G = C$$

Question 17

If the percentage of guanine in a DNA sample is 17.7%, what is the expected percentage of cytosine?

Accepted Answer

17.3%

Question 18

Which real-world application relies on the unique sequence of DNA bases?

Accepted Answer

DNA fingerprinting in forensic science

Question 19

What would happen in the Hershey-Chase experiment if proteins carried the genetic information?

Accepted Answer

Radioactive sulfur would be found inside the cells

Question 20

Which feature of the DNA double helix allows for the storage of genetic information in a vast variety of sequences?

Accepted Answer

The base-pairing rules do not restrict the sequence of nucleotides along each strand

The Discovery of DNA as the Genetic Material

Study Guide - Practice Questions