1. DNA structure DNA is made of subunits called Nucleotides
Nucleotides are made of 3 parts
1) one 5 carbon sugar
2) phosphate
3) nitrogen containing base

2. Nucleotides are bonded together in long chains
Strong covalent bonds hold one nucleotide to the next
The strong bonds between
phosphates & sugars forms
backbone of the double helix

3. The double helix shape is formed when
2 chains of nucleotides are stuck together by weak
Hydrogen bonds between their bases

4. The two joined strands are twisted into a double helix.
Cells store DNA wrapped around proteins called histones
Further wrapping of DNA forms the X-shape
Seen in mitosis

5. Cells can Reproduce by dividing in 1/2
Before dividing cells need to make a copy of their DNA
So that each cell can get one copy
The process used to copy the DNA is called
Semiconservative replication

7. Semiconservative Replication
One double helix is copied so there are 2 double helixes.
1 molecule of DNA becomes 2 molecules of DNA
Each molecule retains one of the original chains of nucleotides
And has one new chain of nucleotides formed by replication

8. Parent vs Daughter Strands
Original chains of nucleotides = Parent strand.
New chain of nucleotides = daughter strands
Daughter strands are complimentary to parent strands
Two new molecules are
Identical
The two strands are antiparallel (face in opposite directions)

9. Helicase – breaks H-bonds between bases and unwinds double helix
Replication Enzymes
Helicase – breaks H-bonds between bases and unwinds double helix
DNA polymerase – assembles new nucleotides on daughter chain of nucleotides covalently bonds them in place

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