explain the relationship between genes, proteins and phenotype with respect to the: • TYR gene, tyrosinase and albinism • HBB gene, haemoglobin and sickle cell anaemia • F8 gene, factor VIII and haemophilia • HTT gene, huntingtin and Huntington’s disease

describe the structure of a molecule of haemoglobin as an example of a globular protein, including the formation of its quaternary structure from two alpha (α) chains (α-globin), two beta (β) chains (β-globin) and a haem group