1. Deoxyribonucleic acid
DNA
Deoxyribonucleic acid

2. DNA is a nucleic acid A nucleic acid is a polymer of nucleotides
A nucleotide is made from a phosphate, sugar and base.

3. Phosphate From phosphoric acid

4. Sugar Deoxyribose in DNA (Ribose in RNA)

5. Base

6. Purines

7. Pyrimidines

8. Nucleotide
Condensation between the phosphate and sugar (at C5) and between the sugar (at C1) and base

9. Dinucleotide Two nucelotides join by condensation
Condensation gives phospho diester bridge

10. Polynucleotide Up to 5 x 106 nucleotides long 5’ end 3’ end
5’ end
3’ end

11. DNA double helix
The bases of the DNA nucleic acid form H bonds to bases of a second molecule of DNA

12. Table from Biological Science – Green, Stout, Taylor

13. A is the same amount as T
G is the same amount as C
Amount of purines equals the amount of pyrimidines
A always bonds to T
G always bonds to C

14. A bonds to T with two hydrogen bonds
G bonds to C with three hydrogen bonds.

15. The two nucleic acids wind into a double helix, with H bonds between polar groups of sugars keeping the shape of the helix.
(diagram from Bioligical Sciences, green, Stout & Taylor)

17. The two strands are ANTIPARALLEL
i.e. they are parallel, but run in opposite directions.

19. Arrangement of DNA in chromosomes

20. Histones in nucleosome
DNA is wrapped around a group of 8 histone proteins and held together by another histone molecule

21. Nucleosomes:
Help in supercoiling of DNA
Help to regulate transcription