[OLD] DNA - Replicating DNA

Question 1

What do you need to replicate DNA?

Answer 1

Nucleotides
Enzymes
Chemical energy (ATP)

Question 2

STEP 1

Answer 2

Helicase unwinds the helix and causes the 2 strands of DNA to separate

Question 3

STEP 2

Answer 3

Free nucleotides in the nucleoplasm are attracted to their complimentary base pairs

Question 4

STEP 3

Answer 4

The strong sugar backbone is rejoined by DNA polymerase, forming identical strands

Question 5

why does DNA polymerase move is opposite ways along anti parallel strands?

Answer 5

each end of a DNA stand is slightly different in structure
one end is the 3’ end and one end is the 5’ end
the active site of DNA polymerase is only complementary to the 3’ end
therefore the enzyme can only add nucleotides to the new strand at the 3’ end
this means DNA polymerase runs down the strand in a 3’ to 5’ direction so the new strand is made in a 5’ to 3’ direction
because the strands 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

Question 6

Why does DNA polymerase work in opposite directions on the 2 different strands?

Answer 6

The strands are in a double helix.
The shape of the nucleotides are different.
Enzymes have active sites with specific shapes.
Only substances with complementary shapes can bind with active site of enzyme.