DNA Replication description

DNA Replication

Academic year: 2023/2024

Uploaded by:

Anonymous Student

This document has been uploaded by a student, just like you, who decided to remain anonymous.

Griffith University

Comments

Please sign in or register to post comments.

Preview text

DNA Replication

The original or parent DNA molecule untwists.
The weak hydrogen bonds of the parent DNA molecule break causing the two strands to separate (or unzip).
Free DNA nucleotides within the cell pair with their complementary nucleotide on the unzipped strands. Hydrogen bonds form joining the bases.
The nucleotides are joined by sugar phosphate bonds and a new DNA strand is formed.
Two identical daughter strands are formed each containing:

one strand from the parent molecule one newly synthesised strand

Requirements for DNA replication

For DNA replication to take place all of the following must be present:

DNA to acts as a template
a supply of all four DNA nucleotides
enzymes to control the process –

Helicase untwists DNA molecule and separates DNA strands (steps 1 and 2)
DNA Polymerase joins the nucleotides together (by joining sugar to phosphate) once base paired (step 4)

ATP for energy for polymerase to join the nucleotides together to form the new sugar- phosphate backbone.

But it is not that simple!: Okizaki fragments

The two strands of DNA are in opposite directions (and the directions are described by 5’ and 3’ ends).

DNA polymerase only joins bases in the 5’ -> 3’ direction.

This means that as the replication fork moves forward, one strand of the DNA can be continuously replicated (called the leading strand).

The other strand (the lagging strand) can only be replicated in short sections, once there are enough bases free to use as a template

These short sections are called “Okizaki fragments”.

They are joined together to make a continuous strand by another enzyme - LIGASE

Importance of exact DNA replication to the cell

 DNA replication produces an exact copy of the organism’s genetic information

 All cell divisions require DNA replication to ensure the daughter cells contain their genetic information for their correct functioning/survival.

 This method of DNA replication ensures that a complete and exact copy of the genetic information is passed onto new cells and the next generation. Therefore, all cells contain all the information (in the form of genes) for them to survive.

 If mistakes (mutations) occur, the cell may not be able to function properly and die ☹

DNA Replication

1. The original or parent DNA

molecule untwists.

2. The weak hydrogen bonds of

the parent DNA molecule break

causing the two strands to

separate (or unzip).

3. Free DNA nucleotides within

the cell pair with their

complementary nucleotide on

the unzipped strands.

Hydrogen bonds form joining

the bases.

4. The nucleotides are joined by

sugar phosphate bonds and a

new DNA strand is formed.

5. Two identical daughter strands are formed each containing:

one strand from the parent molecule

one newly synthesised strand

Requirements for DNA replication

For DNA replication to take place all of the following must be present:

1. DNA to acts as a template

2. a supply of all four DNA nucleotides

3. enzymes to control the process –

-Helicase untwists DNA molecule and separates DNA strands (steps 1 and 2)

-DNA Polymerase joins the nucleotides together (by joining sugar to phosphate)

once base paired (step 4)

4. ATP for energy for polymerase to join the nucleotides together to form the new sugar-

phosphate backbone.

Human Reproductive Biology (BMS406)

Charles Sturt University

Comments

Students also viewed

Related documents

Preview text

DNA Replication

They are joined together to make a continuous strand by another enzyme - LIGASE

Importance of exact DNA replication to the cell