DNA Replication Flashcards
What does DNA have to do? And why?
It has to be able to make exact copies of itself to :
- Allow the organism to grow
- To repair itself
What is Replication?
The process by which DNA makes an exact copy of itself.
What does replication occur to?
Replication occurs prior to cell division.
What is a replication fork?
When DNA unwinds and unzips it opens out into a Y shape. This is known as a replication fork.
What does DNA replication involve?
Many enzymes
Describe what DNA polymerase does?
- It adds complementary nucleotides to the deoxyribose sugar (3’) end of a DNA strand.
- It also forms the strong chemical bonds needed for the sugar phosphate backbone.
- Since DNA polymerase can only add nucleotides to the 3’ end, the replication of each template strand runs in the opposite direction to each other.
What is the name of each strand of DNA?
The leading strand
The lagging strand
Describe the leading strand?
Replication of DNA from the 3’ end is continuous moving towards the junction of the replication fork.
Replication from the 5’ end is discontinuous moving away from the replication fork,
Describe the process of replication of the leading strand?
- After the hydrogen bonds break, the DNA unzips.
- A DNA primer attaches to the start of the piece of DNA to be copied.
- DNA polymerase then attaches free nucleotides to the 3’ end of the primer.
- This continuous process continues until the leading strand is copied.
What is a primer?
A short stretch of complementary DNA
Describe the process of replication of the lagging strand?
- Many primers attach along the strand
- DNA polymerase attaches nucleotides to these primers to form fragments.
- The fragments are then joined by the enzyme ligase.
- This is a discontinuous process creating the lagging strand.
What are the requirements for replication?
There must be a supply of:
- DNA (template)
- Primers
- Supply of free DNA nucleotides
- Appropriate enzymes (DNA polymerase and ligase)
- ATP
