Key Area 1.2 - DNA Replication Process Flashcards
What happens just before a cell starts the DNA Replication process?
The DNA must be replicated (copied) using the enzyme DNA polymerase
What is the first stage in DNA replication?
DNA double helix unwinds and weak hydrogen bonds between base pairs break (to form 2 template strands)
What is the second stage in DNA replication?
DNA template strands become stabilised and expose their bases at a y-shaped replication fork
What is the third stage in DNA replication?
One strand of the replication fork is a template for the Leading Strand and the other is the template for the Lagging Strand
What is the fourth/fifth stage in DNA replication (First Leading Strand Stages)?
Replication of the DNA template strand that has the 3’ end exposed is continuous and forms the replicated DNA.
The DNA primer binds to the 3’ end of the template DNA which allows DNA Polymerase to add DNA Nucleotides
What is the sixth/seventh stage in DNA replication (Last Leading Strand Stages)?
Free DNA bases align with complementary base pairs on the template strand and become bound to the deoxyribose 3’ end of the primer.
(DNA Nucleotides can only be added to its 3’ end)
DNA Polymerase brings about the formation of the sugar-phosphate bonds between the primer and the nucleotides. This results in the Leading Strand being replicated continuously.
What 5 substances are required for DNA Replication?
DNA, Ligase, ATP, DNA Nucleotides and Primers
Why do cells need to carry out DNA Replication?
For cells to pass on an exact copy of genetic information during growth or reproduction
How are nucleotides joined to the DNA strand?
By sugar - phosphate bonds
What are replication forks and why is it better to use more than one of them?
They are the location where bases between DNA strands are broken and DNA replication takes place. More than one speeds up the replication of DNA.
What is the eighth stage in DNA replication (First Lagging Strand Stage)?
Replication of the DNA template strand that has the 5’ end exposed is discontinuous (as it has to be replicated in fragments starting with the 3’ end of a primer)
What is the ninth/tenth stage in DNA replication (Last Lagging Strand Stages)?
Each fragment has to be primed to allow DNA Polymerase to add DNA Nucleotides.
Once replication of a fragment is complete, Ligase Enzyme joins the fragments together to create the Lagging Strand of DNA.
