DNA Replication Alevel Book Flashcards
What type of replication is DNA replication
Semi conservative replication
What is semi conservative replication
When half of the strands in each new DNA molecule are from the original DNA molecule
What does semiconservative replication result in between generations of cells
Genetic continuity
What do we refer to the direction in which DNA polymerase moves along the DNA strands
Anti parallel,5’ to 3’. And 3’ to 5’
What is unique about the 3’ end of the newly forming DNA strand
The active site of DNA polymerase is only complementary to the 3’ end of the newly formed DNA strand.
So the enzyme can only add nucleotides to the new strand at the 3’ end
At what stage of the cell cycle does DNA replication occur
S phase (synthesis phase)
What does semi conservative mean
This means that each strand acts as a template and that each new molecule of DNA contains one original strand and one new strand
What are the enzymes DNA replication requires
DNA helicase and DNA polymerase
What is the role of DNA helicase
Unwinds DNA and breaks hydrogen bonds between bases. This allows nucleotides to attach to each strand and for each strand to act as a template
What is the role of DNA polymerase
Join adjacent nucleotides together,forming phosphodiester bonds in the sugar-phosphate backbone
What is the first stage of DNA replication
DNA helicase separates the DNA strands by breaking the hydrogen bonds
What is the second stage if DNA replication
Each strand acts as a template
What is the third stage of DNA replication
Free nucleotides attach to the exposed bases by complementary base pairing
What is the fourth stage of DNA replication
DNA polymerase joins nucleotides (on new strands) forming a phosphodiester bonds
What direction are new DNA strands replicated in
The 5’ to 3’ direction
