Replication, Mutations, and PCR

Question 1

Replication

Answer 1

DNA copies are made using the DNA molecule itself as a template
* origin of replication - sites where the two DNA strands separate. Replication “bubble” opens
* Replication proceeds in both directions, until entire molecule is copied

Question 2

Prokaryotic chromosome

Answer 2

one origin of replication

Question 3

Eukaryotic chromosome

Answer 3

may have hundreds or thousands of origins of replication

Question 4

Replication Fork

Answer 4

a Y-shaped region where new DNA strands are elongating at the end of each replication bubble
Nucleotides can only be added by DNA polymerase to 3’ end of a nucleic acid molecule
* Leading Strand -copied in one piece behind the opening replication

Question 5

leading strand

Answer 5

copied in one piece behind the opening replication fork

Question 6

lagging strand

Answer 6

DNA polymerase must work in the direction away from the replication fork.
* synthesized as a series of Okazaki fragments
* which are joined together by DNA ligase

Question 7

helices

Answer 7

are enzymes that untwist the double helix at the replication forks

Question 8

single-strand binding proteins

Answer 8

bind to and stabilize single-stranded DNA

Question 9

primase

Answer 9

makes an RNA primer for DNA polymerase III to work from

Question 10

DNA Polymerase III

Answer 10

builds a nucleic acid adding nucleotides to the 3’ end of the growing molecule

Question 11

DNA ligase

Answer 11

join Okazaki fragments after the RNA primer is replaced

Question 12

DNA polymerase I

Answer 12

replaces the RNA fragments in the lagging strand with DNA

Question 13

Topoisomerase

Answer 13

relieves the strain of twisting of the double helix by breaking, swiveling, and rejoining DNA strands

Question 14

nuclease

Answer 14

cuts out and replaces damaged stretches of DNA in DNA repair nucleotide excision repair

Question 15

mismatch repair of DNA

Answer 15

repair enzymes correct errors in base pairing

Question 16

telomeres

Answer 16

special nucleotide sequences at the ends Eukaryotic chromosomal DNA molecules
* don’t prevent the shortening of DNA molecules, postpone the erosion of genes near the ends of DNA molecules
* the shortening of telomeres may be connected to aging