2. DNA Replication

Question 1

why called semi-conservative replication

Answer 1

each new DNA molecule contains 1 strand from original DNA molecule and 1 new strand

Question 2

Process

3 steps

Answer 2

1. enzyme DNA helicase breaks H bonds between bases. helix unwinds into 2 single strands
2. each original strand is template for new strand. complimentary base pairing = free floating DNA nucleotides attracted to complimentary exposed bases
3. condensation reaction joins nucleotides of new strands. catalysed by enzyme DNA polymerase.
   H bonds form between bases of original and new strands.

Question 3

why does DNA polymerase move in opposite ways along antiparallel DNA strands

Answer 3

Active site of DNA polymerase only complimentary to 3’ end
enzyme can only add nucleotides to strands at 3’ end
new strand made in 5’ to 3’ direction
template strands in 3’ 5’ direction (strands antiparalel)

Question 4

how is each end of DNA strand different structure

Answer 4

one end 3’ one end 5’