DNA replication

Question 1

What does DNA replication do and when does it happen?

Answer 1

Produces two identical copies of the
chromosome during S phase of
interphase.

Question 2

DNA replication is catalyzed by many..

Answer 2

enzymes

Question 3

The structure of DNA allows it to be easily…….

Answer 3

replicated

Question 4

_________ between base pairs can be broken (unzipped) and each strand acts as a ________ for adding new nucleotides.

Answer 4

H-bonds, template

Question 5

What are the three steps of replicating DNA?

Answer 5

Separating the DNA strands

Building complementary strands

Linking of Nitrogenous Bases

Question 6

What happens in the first step of DNA replication, separating the DNA strand?

Answer 6

Initiated at sites along DNA called
Replication Origins – made of
specific nucleotide sequences

Enzymes and other proteins work
together to unwind and stabilize the
double helix

Question 7

What are the players/enzymes in step one (separating the DNA strand) in DNA replication?

Answer 7

DNA helicase

DNA gyrase

SSBs

Question 8

What does DNA helicase do?

Answer 8

Recognizes specific nucleotide
sequence (origin of replication)

Unwinds double helix by breaking H
bonds between complementary base
pairs

Opens up replication bubble

Question 9

What does DNA Gyrase do?

Answer 9

Relieves the tension produced by
the unwinding of DNA

Question 10

What does SSBs (Single-stranded Binding Proteins) do?

Answer 10

Keep separated DNA strands apart
by blocking hydrogen bonding

Keep the templates (single DNA
strands) straight

Question 11

What is the replication fork?

Answer 11

The junction where the DNA strands
are still joined

Question 12

What happens during the second step of DNA replication (Building complementary strands)?

Answer 12

Replication begins in two directions
from the origin(s) as a region of DNA is unwound

Replication proceeds towards the
replication fork on one strand, and away from the fork on the other strand.

Question 13

Because there may be
more than one origin of
replication in eukaryotes,
more than one ___________ _____ may exist.

Answer 13

replication fork

Question 14

What are the players in the second step of DNA replication (Building complementary strands)?

Answer 14

DNA polymerase

primase

DNA ligase

Question 15

What does DNA polymerase III?

Answer 15

Takes free nucleotides found
within the cell and adds them in the
5’ to 3’ direction

The parent strand is used as a
template

Question 16

What is the leading strand what does it do?

Answer 16

The daughter strand that grows
continuously towards the replication
fork as the double helix unwinds

Occurs quickly

Requires a single RNA primer

Question 17

What is the lagging strand in DNA replication?

Answer 17

Built in short segments (in the 5’ to 3’ direction) away from the replication
fork

Requires many RNA primers

Question 18

Why is the 3’ to 5’ strand a problem for DNA polymerase?

More details for lagging strand.

Answer 18

The 3’ to 5’ parent strand is a problem for DNA polymerase since it must synthesize in the 5’ to 3’ direction.

Question 19

What does Primase do in the second step of DNA replication (Building complementary strands)?

Answer 19

Builds RNA primers (used to initiate DNA replication)

Question 20

What are Okazaki Fragments?

Answer 20

Short fragments of DNA built by
DNA polymerase off of the RNA
primers

Question 21

What does DNA Polymerase I do in step two of DNA replication?

Answer 21

Removes the RNA primers once they
have been used and replaces them with the appropriate DNA sequence

Question 22

What does DNA ligase do in step two of DNA replication?

Answer 22

Joins the Okazaki fragments into one
strand by the creation of phosphodiester bonds

Question 23

What happens in step 3 of DNA replication (Linking Nitrogenous Bases) ?

Answer 23

Nitrogen bases of nucleotides of
opposite strands (parent and daughter)
form new H bonds

Once bonds are formed, DNA twists
automatically into a double helix

Question 24

Why is DNA polymerase consider the quality controller enzyme thingy

Answer 24

DNA polymerase acts as a
proof-reader by checking the newly
synthesized strand for any incorrectly inserted bases

Question 25

If a mistake is found, act as an
___________ – & cut out the mistake

Answer 25

exonuclease