1. Structure and Replication, replication, replication, replication
DNA
Structure
and
Replication, replication, replication, replication

2. Building block of DNA the Nucleotide
1 phosphate
1 deoxyribose sugar
1 of 4 nitrogen bases
Adenine A
Thymine T
Cytosine C
Guanine G

3. The back bone of the DNA Ladder
Sides of the DNA Ladder are made of:
Phosphate molecules
Deoxyribose sugars: five sided sugars missing one oxygen

4. Number the carbons
The carbons in the deoxyribose sugar are numbered clockwise. The phosphodiester bond occurs between the 5’ carbon of one sugar and the 3’ carbon of the next sugar.

5. Linkage
This back bone of DNA is linked together by strong covalent bonds called Phosphodiester bonds. This is done by removing a water molecule

6. Antiparallel Strands in the Double Helix
The rungs of the ladder are nitrogen base pair.
To ensure they are pointing towards the middle
The sides of the ladder are going in opposite directions.
This is called antiparallel.
Look at the #s on the carbons at
the end of each strand.
We call this the three prime 3’ end
And a five prime 5’ end.

7. The rungs of the ladder complimentary
The rungs of the DNA double helix are held together by weak hydrogen bonds. They are easily made and easily broken.
G always pairs with C
3 h-bonds
A always pairs with T
2 h-bonds
This is called complimentary base
pairing
A & G have 2 rings (Purines) and C&T have 1 ring (Pyrimidines)
This ensure that the rungs of the ladder are always 3 rungs wide

8. Now you know DNA Deoxyribonucleic acid is: Double helix Antiparallel
And complimentary
Soon you will also learn…
It is semi conservative.

9. Replication Make new friends but keep the old one is silver and the other gold
DNA has 2 things that it can do:
Copy itself Replication
Make proteins Protein synthesis
Replication is semi-conservative. DNA uncoils and each of the old strands makes a new complimentary copy.

10. Enzymes the body’s workers
Every step of the DNA replication is helped by and enzyme.
Enzymes are proteins that speed up reactions. They end in “-ase”.
Helicase Unwinds the double helix by breaking the hydrogen bonds

11. 2.Binding proteins hold the replication fork open

12. 3. Primer is attached to 3’end and provides a place for polymerase to attach.

13. 4. Polymerase
Just for fun here’s what it looks like.

14. Polymerase can extend the new DNA strand by adding free floating base pairs to the 3’ end.

15. Polymerase can also proof read and fix mistakes

16. Leading strand and lagging strand.
Because Polymerase can only add to a 3’ end one side of the DNA is copied in a continuous strand. This is the leading strand.
The other side has to restart over and over as the DNA uncoils.
laying down a new primer and a short piece of DNA each time.
It looks like a dotted line. This is the lagging strand and the pieces are Okazaki fragments.

18. 5. Ligase Ligase follows along after polymerase.
It makes the phosphodiester bonds in the back bone.
It and ties the Okazaki Fragments together on the lagging strand.
Here it is in a nut shell.

20. Tah Dah!