DNA is composed of nucleotide bases which can be sequenced to code for specific amino acids. The bases are A,T,G and C and each base will pair in a ladder known as a double helix. A section of DNA in the strand is known as a chromosome with a centromere for spindle fibres (required for cell division).

The complete set of alleles is the complete genetic make-up for the organism, known as the genotype. This is largely responsible for all of the physical features of the organism which are known as the phenotype.