ABSTRACT
Each v e rteb ra te host is a m ulticellu lar organism com posed o f tens o f m illions o f cells. M ost cells form tissues and organs b u t each cell has at som e stage o f its life a nucleus w hich contains a set o f chrom osom es specific to each organism — the genotype. The genes (m ade up o f D NA ) are located on the chrom osom es and contain the ‘b lu e p r in t’ for all the p ro tein m olecules tha t are assem bled in to an individual.
