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GENE EXPRESSION Three requirements for production of DNA and RNA. 1. Monomers: nucleotides 2. Energy: to form the chemical bonds 3. Information: to ensure nucleotides are assembled in the correct order Nucleotides: contain a sugar, nitrogenous base and a phosphate. There are 2 different types of nitrogenous bases: 1. Purines: A & G 2. Pyrimidines: C & T The purine or pyrimidine is are linked to the sugar by glycosidic bonds to form nucleosides. Nucleotides are phosphoric esters of nucleosides and the phosphate is joined to C 5 hydroxyl of the ribose or deoxyribose. Nucleotides are joined together by phosphodiester linkages between the 5’ phosphate group on one nucleotide and the 3’ –hydroxyl group on the sugar residue of the next nucleotide. Oligonucleotide = a short nucleic acid (50 or less nucleotides) Strand separation is complicated by the fact that DNA is plectonemic meaning the two strands are wound around each other. Differences between RNA and DNA 1. 2 – deoxy – D – ribose in DNA and D-Ribose in RNA 2. RNA contains the pyrimidine uracil instead of thymine 3. RNA usually exists as a single strand DNA REPLICATION IN BACTERIA Three DNA polymerases have been identified in E.
Approximate Word count = 778
Approximate Pages = 3.1
(250 words per page double spaced)
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