Topic 1---B- More biological molecules- 2. DNA replication Flashcards
1
Q
Why is it called semi-conservative replication?
A
Because half of the strands in each new DNA molecule are from the original DNA molecule.
2
Q
How is DNA replicated? (stages)
A
- The enzyme DNA helicase breaks the hydrogen bonds between the complementary base pairs on the 2 polynucleotide DNA strands.
- This makes the helix unwind to form two single strands.
- Each original single strand acts as a template for free nucleotides to align with their complementary base.
- DNA polymerase forms phosphodiester bonds between adjacent nucleotides
3
Q
What is the action of DNA polymerase?
A
- Each end of a DNA strand is different in it’s structure.
- One end is called the 3 prime end and one end is called the 5 prime end.
- During DNA replication the active site of the DNA polymerase is only complementary to the 3 prime end ( only 1 direction)
- So because the strands in the double helix are anti-parallel the DNA polymerase working on one of the template strands moves in the opposite direction to the DNA polymerase working on the other template strand.
4
Q
Whp came up with the theory of semi-conservative replication?
A
Watson and Crick
5
Q
Who showed DNA is replicated using the semi-conservative method?
A
Meselson and Stahl’s
