DNA Replication

Mackenzie Atcheson

DNA Replication begins in the Origin of

Replication.This is Called the Replication Fort.

Adenine

5’

5’

Adenine

Thymine

5’

5’

Adenine

Thymine

Cytosine

5’

5’

Adenine

Thymine

Cytosine

Guanine

5’

5’

3’

3’

5’

5’

Adenine

Thymine

Cytosine

Guanine

3’

3’

5’

5’

Adenine

Thymine

Cytosine

Guanine

AdenineA purine base,

that is the constituent involved in

base pairing with thymine in DNA and

with uracil in RNA.

A

A

A

3’

3’

5’

5’

Adenine

Thymine

Cytosine

Guanine

Thyminea pyrimidine base that is one of the four bases

coding genetic

information in the

polynucleotide chain of DNA

A

A

A

T

T

T

3’

3’

5’

5’

Adenine

Thymine

Cytosine

Guanine

Cytosinea pyrimidine

base that codes genetic information in

the polynucleotide chain of DNA

or RNA

A

A

A

T

T

T

C

C

3’

3’

5’

5’

Adenine

Thymine

Cytosine

Guanine

Guaninea purine base

that codes genetic

information in the

polynucleotide chain of DNA

or RNA

A

A

A

T

T

T

C

C

G

G

3’

3’

5’

5’

Adenine

Thymine

Cytosine

Guanine

DNA Polymerase

Reads DNA

In The 3’-5’

Direction.

A

A

A

T

T

T

C

C

G

G

Helicase

The first step of DNA replication is unwinding or unzipping the DNA. Helicase is the enzyme that unzips the DNA.

A

A

A

A

T

T

T

T

G

G

G

G

C

C

C

C Hydrogen Bonds between the base pairs are broken.

5’

5’

A

A

A

A

T

T

T

T

G

G

G

G

C

C

C

C

A molecule of DNA Polymerase attaches to one strand of the DNA and moves in the 3’ to 5’ direction.

5’

5’

A

A

A

A

T

T

T

T

G

G

G

G

C

C

C

C

A molecule of DNA Polymerase attaches to one strand of the DNA and moves in the 3’ to 5’ direction.

This is used as a template for assembling a leading strand of nucleotides and reforming the double helix.

5’

5’

A

A

A

A

T

T

T

T

G

G

G

G

C

C

C

C

DNA synthesis can only occur in a 5’ to 3’ direction.

5’

5’

A

A

A

A

T

T

T

T

G

G

G

G

C

C

C

C

DNA synthesis can only occur in a 5’ to 3’ direction.

Another form of DNA polymerase binds to the other strand.

5’

5’

A

A

A

A

T

T

T

T

G

G

G

G

C

C

C

C

This molecule must synthesize discontinuous segments of polynucleotides

5’

5’

A

A

A

A

T

T

T

T

G

G

G

G

C

C

C

C

This molecule must synthesize discontinuous segments of polynucleotides

These are called Okazaki Fragments.

5’

5’

There are now two identical copies of the DNA.

Thymine—Adenine

Guanine—Cytosine

BASE PAIRSSugar Phosphate Backbone

Thymine—Adenine

Guanine—Cytosine

BASE PAIRSSugar Phosphate Backbone

DNA Replication occurs in the “S” phase of the interphase in mitosis.

THE END