1. Nucleic Acids Individual unit called a (mono)nucleotide
Polymer
Individual unit called a (mono)nucleotide
DNA is a type of nucleic acid
deoxyribonucleic acid

2. DNA is a polymer made up of individual units called nucleotides

3. Nucleotide Structure 3 components: Pentose sugar Organic base
Phosphate
sugar
base
Stay the same
Changes
Contains nitrogen & carbon
Pentose sugar
(5 Carbon atoms)
3 components:
Pentose sugar
(ribose in DNA)
Phosphoric acid
Organic base
(always contains nitrogen)

4. 4 Bases Purines – Pyrimidines – Double ringed structure
Single ringed structure

5. Bondings The base and sugar join with a: glycosidic bond
The phosphate and sugar join with an:
ester bond
Both require a condensation reaction to occur 

6. 2 condensation reactions occur in the formation of a nucleotide:
Phosphate
2 condensation reactions occur in the formation of a nucleotide: H
Ester bond OH
Glycosidic
bond OH H
Base
Sugar

8. Tell me… 4 names of bases in DNA 3 components of a nucleotide
2 ends of a strand are called
1 place where a condensation reaction occurs
2 types of bonds in a nucleotide
1 difference between purine and pyrimidine bases

9. Compl mentary Base Pairing
*Purines always pair with pyrimidines*
A joins to T (2 hydrogen bonds)
C joins to G (3 hydrogen bonds)
Therefore, when discussing the proportions of a particular base, you will always find A=T and C=G
or! A+C = G+T
see e

10. Bonding relationships
Type of Base
Purine
Pyrimidine
Structure
Bonding relationships
Adenine
Guanine
Thymine
Cytosine
= hydrogen bond

11. 5’
3 hydrogen bonds 3’ C G
0.34nm A T 3’
2 hydrogen bonds 5’
2nm

12. Phosphodiester Bonds: the sugar-phosphate-backbone

13. G 5’ C 3’ C G T 3’ 5’ T 0.34nm A A 3C 5C 5C 3C 5C 5C 3C 5C 5C 3C 3C 5C

14. G C C G T T 5’ 3 hydrogen bonds 3’ 0.34nm 2 hydrogen bonds A 3’ A 5’

15. Strands run anti parallel

16. Points to remember: nucleotides DNA stands for deoxyribonucleic acid
It is a polymer of mono
Each nucleotide has three components:
pentose sugar (deoxyribose)
phosphate group
organic base (4 types - purines/pyrimidines)
2 condensation reactions occur when the
base and sugar form a glycosidic bond
phosphate and sugar form an ester bond
Phosphodiester bonds build a sugar phosphaphate backbone on each strand of DNA, with the bases all facing inwards
The 2 strands of the DNA molecule form anti-parallel to one another; one strand runs 5’ to 3’ and the other strand runs 3’ to 5’
The strands wind around one another into a double helix (like a twisted ladder)
nucleotides

17. 4 Bases Purines – Pyrimidines – Double ringed structure
Single ringed structure

18. DNA Replication – why?
DNA carries the genetic code in the order of its bases (more info to come)
To pass this information on the molecule needs to replicate itself
DNA replication always occurs just before mitosis. This way the cell can make an exact copy of itself
When might this occur in the cell?

19. Movie time! http://207.207.4.198/pub/flash/24/menu.swf
Key words to look out for:
Replication fork
Template
Complementary base pairing
Leading strand
Lagging strand
Okazaki fragments
Enzymes:
helicase
dna polymerase
ligase

20. Summarise into 3 stages

21. Semi-conservative Replication
½ of the old strand of DNA is conserved in each new strand and the 2 new strands are identical