biology
- Created by: smileyface
- Created on: 23-05-11 08:31
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- Individual nucleotides of DNA are made up of 3 components
- Deoxyribose sugar
- Phosphate group
- Organic base
- Single ring base - so it can be cytosine and thymine
- or it can be a double ring base - Adenine and guanine
- the 3 components are joined together by a condensation reaction ---> 1 nucleotide
- two mononucleutides are combined to form a dinucleoutide
- Linking of mononucleutides forms a long chain called a polynucleutide
DNA STRUCTURE
- DNA is made up of 2 strands (joined by hydrogen bonds)
- DNA can be thought of as a ladder in which the phosphate group and the deoxyribose alternate to form the uprights and organic base pairs to form the rungs
PAIRING OF BASES
- Organic bases contain nitrogen and are of 2 types
- double ring structures have longer molecules than single ring bases
- Therefore if the DNA is to be of the same length then there has to be one double ring base and one single base ring
- As a result A + T bind together ... 2 hydrogen bonds
- and G + C bind together ... 3 hydrogen bonds
- THEREFORE, THESE BASE PAIRINGS ARE COMPLIMENTORY
- The ratio of Adenine- Thymine : Guanine-Cytosine vary in species
double helix
- ladder like arrangement
- 2 polynucleutide…
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