Nucleic acid structure, semi-conservative replication, the genetic code, transcription and translation, and the effect of mutations.
DNA stores the genetic code; RNA helps express it. Both are polymers of nucleotides.
Nucleotide and DNA structure
A nucleotide = a pentose sugar + phosphate + nitrogenous base. In DNA the sugar is deoxyribose and the bases are adenine, thymine, cytosine, guanine. Nucleotides join by phosphodiester bonds (sugar–phosphate backbone). Two strands run antiparallel in a double helix, held by hydrogen bonds between complementary bases: A–T (2 bonds) and C–G (3 bonds). RNA is single-stranded, contains ribose, and uses uracil instead of thymine.
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