A1.2 Nucleic Acids

Nucleotides

Nucleotides

The monomers that make up nucleic acids through a series of condensation reactions called polymerization.

• Phosphate group

• Pentose sugar

• Nitrogenous base

• Covalent bond between phosphate group attached to 5’C of one pentose sugar and the hydroxyl group attached to the 3’C of another sugar, releasing one molecule of water with the use of energy.

Chargaff’s rule

In any sample of DNA, the amount of adenine = amount of thymine, and the amount of cytosine = amount of guanine.

Purines

Nitrogenous bases that have two rings in their structure.

Pyrimidines

Nitrogenous bases that have one ring in their structure.

Nucleosomes

Negatively-charged DNA wrapped twice around a core of 8 positively-charged histone proteins. An additional histone protein attached to linker DNA holds the nucleosome together.