Notes: DNA Replication Topic 2

During the S phase of Interphase (Cell Cycle) the DNA must replicate itself so that when the cell divides each new daughter cell will receive an exact copy of the original DNA code.

Steps in DNA Replication 1 - Helicase (Enzyme) breaks the hydrogen bonds between nitrogen bases and unwinds the two DNA strands

2 - Complimentary Base Pairs attach by 2 - Complimentary Base Pairs attach by hydrogen bonds to newly exposed base pairs on the DNA strand. base pairs are complimentary: A - T and C - G they will always pair up the same way.

3 - DNA polymerase synthesizes the new nucleotides together.

DNA replication is semi-conservative. Each replicated strand of DNA is made of one new strand and one original strand.

Helicase Breaks Hydrogen Bonds T C A T G

Helicase Breaks Hydrogen Bonds and DNA stands seperate

Helicase Breaks Hydrogen Bonds and DNA stands seperate

DNA polymerase synthesizes new strands of DNA using complimentary base pairs. Original Strand New Strand Original Strand

DNA polymerase synthesizes new strands of DNA using complimentary base pairs. Original Strand New Strand Original Strand

DNA polymerase synthesizes new strands of DNA using complimentary base pairs. Original Strand New Strand Original Strand

DNA replication produces two new identical strands through semi-conservative replication.

Assignment: Cut your original drawing of DNA, separating the nitrogen bases (your scissors will act like helicase) Replicate the two new strands of DNA onto your two original strands (your hand will act like DNA polymerase). A T C G A T T A C G