1.4.10 Describe the basic structure of mononucleotides (as a deoxyribose or ribose linked to a phosphate and a base, i.e. thymine, uracil, cytosine, adenine or guanine) and the structures of DNA and RNA (as polynucleotides composed of mononucleotides linked through condensation reactions) and describe how complementary base pairing and the hydrogen bonding between two complementary strands are involved in the formation of the DNA double helix.

- Nucleotides contain a phosphate group, a base ( either a purine: adenine & guanine or a  pyrimidine: thymine, uracil and cytosine), and a pentose sugar (deoxyribose/ ribose) joined in a condensation reaction, the phosphate joins to carbon 5 of the sugar and the base joins to carbon one. 

- Nucleotides are joined in a condensation reaction between the sugar of one nucleotide and the phosphate group of the other nucleotide via phosphodiester bond.

- Many nucleotides join together to form single stands in RNA, complimentary base pairing allows hydrogen bonding between bases holding DNA in a double stranded structure, two H bonds form between A and T, three between C and G.