Question 1

Which of the following best explains why most biologists initially believed proteins, rather than DNA, were the genetic material?

Accepted Answer

Proteins have a greater variety of 3D structures and functions than DNA.

Question 2

In Griffith’s experiment with Streptococcus pneumoniae, what was the surprising result that led to the proposal of a 'transformation factor'?

Accepted Answer

Live harmless bacteria became deadly when mixed with heat-killed deadly bacteria.

Question 3

What does transformation involve in bacteria?

Accepted Answer

Assimilation of external DNA into a cell.

Question 4

How did the Watson-Crick model of DNA structure relate to Chargaff’s rules?

Accepted Answer

It explained why $$A = T$$ and $$G = C in $$DNA.

Question 5

If cytosine makes up 38% of the nucleotides in a DNA sample, what percentage of the nucleotides will be thymine?

Accepted Answer

12

Question 6

Which chemical bond is found between paired bases of the DNA double helix?

Accepted Answer

Hydrogen

Question 7

What does it mean that DNA strands are 'antiparallel'?

Accepted Answer

The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

Question 8

Which experiment provided evidence that DNA replication is semiconservative?

Accepted Answer

Meselson and Stahl’s experiment using isotopes of nitrogen.

Question 9

Suppose you add radioactive thymine to a culture of E. coli. After one round of DNA replication, what would you expect?

Accepted Answer

DNA in both daughter cells would be radioactive.

Question 10

A new DNA strand elongates only in the 5' to 3' direction. Why?

Accepted Answer

DNA polymerase can only add nucleotides to the free 3' end.

Question 11

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

Accepted Answer

DNA ligase

Question 12

What determines the nucleotide sequence of the newly synthesized DNA strand during replication?

Accepted Answer

The nucleotide sequence of the template strand.

Question 13

Why does every replication of a linear DNA molecule lead to a shortening of the DNA molecule?

Accepted Answer

DNA polymerase cannot complete the 5' ends of daughter strands.

Question 14

Why are telomeres important to eukaryotic chromosomes but absent in bacteria?

Accepted Answer

Eukaryotic chromosomes are linear and need protection at their ends.

Question 15

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

Accepted Answer

It synthesizes a short RNA primer to provide a starting point for DNA polymerase.

Question 16

Which of the following is a function of topoisomerase during DNA replication?

Accepted Answer

It relieves the strain caused by unwinding of the DNA.

Question 17

Which of the following best explains why simultaneous transcription and translation can occur in bacteria but not in yeast?

Accepted Answer

Bacteria lack a nuclear envelope, so ribosomes can access mRNA as it is being transcribed.

Question 18

Why couldn’t the genetic code be made of codons that have only 2 nucleotides instead of 3 nucleotides?

Accepted Answer

There would not be enough combinations to code for all 20 amino acids: $$4^2 = 16$.

Question 19

Refer to the two electron micrographs provided. Which image most likely represents DNA replication in a eukaryote, and why?

Accepted Answer

The second image, because it shows multiple origins of replication along the DNA.

DNA Structure and Replication: Practice Questions & Step-by-Step Guidance

Study Guide - Practice Questions