Biology 8.1 Structure of DNA

DNA = deoxyribonucleic acid, double helix structure, determines inherited characteristics, contains vast amounts of information (genetic code).

Nucleotide structure

Individual nucleotides of DNA = three basic components:

• a sugar called deoxyribose (pentose sugar)
• a phosphate group
• a nitrogenous base belonging to one of two different groups
• These are: single-ring bases (cytosine and thymine)
• and double ring bases (adenine and guanine)

- Groups combine as a result of a condensation reaction to produce a mononucleotide.

Combined again for dinucleotides and polynucleotides.

NB: Don't get confused between DNA and proteins - DNA = sequence of bases (polynucleotide), proteins = sequence of amino acids (polypeptide).

DNA Structure

DNA = made up of two strands of polynucleotides, each extremely long.

- Two strands joined together by hydrogen bonds between complementary bases.

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