Chapter 16 - DNA Replication

Question 1

Who discovered the structure of DNA?

Answer 1

James Watson and Francis Crick

Question 2

What is the structure of DNA?

Answer 2

Double Helix; they are antiparallel running from 5’ to 3’; adenine binds with thymine and guanine will bind with cytosine.

Question 3

How does a strand of DNA become a chromosome?

Answer 3

Histones will combine together to make a Nucleosome. The DNA strand will wrap around the Nucleosomes and then fold back and forth to make a Chromosome.

Question 4

What are the three models of replication?

Answer 4

Conservative, Semiconservative and Dispersive.

Question 5

What enzymes are needed in DNA replication? and what function do they have.

Answer 5

Helicase - untwists the double helix and separates the strands
Topoisomerase - relieves strain by breaking, swiveling, and rejoining DNA strands, usually comes in front of the DNA strand before it breaks apart.
Primase - Synthesizes primers
DNA polymerases - create new DNA strand by adding nucleotides to existing DNA strand (DNA polymerase I and DNA polymerase III)
DNA ligase - Forms a bond between newest DNA strand and previous DNA strand.

Question 6

What it the defference between DNA Polymerase I and III?

Answer 6

DNA Polymerase I will replace the RNA used as a primer with DNA.
DNA Polymerase III adds DNA nucleotides to the primers set.

Question 7

What are the other molecules used for replication?

Answer 7

Single-strand binding proteins - stabilize the unwound DNA strand
Primer - Piece of RNA binds a specific points and start replication.

Question 8

What happens in Proofreading and Repairing DNA?

Answer 8

Errors in complete DNA molecule ~ 1 in 10 billion

• Proofread by DNA polymerase will remove the error
• Sometimes DNA will go without proofreading 1 in 100,000 times
• DNA repair enzymes - identify and fix