DNA replication Flashcards
What Is the process DNA replication
When a cell goes through cell division, All of its DNA is copied
What occurs in the first stage of DNA replication
The enzyme, DNA helicase attaches to the DNA molecule
What does DNA helicase do
Causes the hydrogen bonds between complimentary bases to break
What happens when the hydrogen bonds between complimentary bases break
The two polynucleotide strands separate from each other
What happens after the polynucleotide strands are separated from each other
Free nucleotides line up with their complimentary bases on the DNA strands
What are the free nucleotides held in place by
The hydrogen bonds between the complimentary bases
What is different about free nucleotides
They are called activated nucleotides
What’s the difference between normal nucleotides and activated nucleotides
An activated nucleotide contains three phosphate groups whilst a normal nucleotide only contains one
What happens once the activated nucleotides are lined up and held in place by hydrogen bonds between the complimentary base pairs
A second enzyme now attaches called DNA polymerase
What does DNA polymerase do
Moves down the molecule and catalyses the formation of a phosphodiester bond between the activated nucleotides
(Condensation reaction)
What happens when the phosphodiester bonds form between the activated nucleotides
The activated nucleotides lose their extra two phosphate groups, as they leave it provides the energy for the reaction
What is semi conservative replication
When each of the DNA molecules contains one strand from the original DNA molecule and one strand is brand new
What happens when an incorrect base is inserted into the growing polynucleotide strand
The DNA sequence has changed
This is called a mutation
How do mutations occur
Random and spontaneously
