The human genome sequence and the analysis of multifactorial traits.

The human genome probably codes for about 10,000 basic functional units, most of which are functionally related families of genes occurring in one or more closely linked clusters. This relatively limited complexity means that a knowledge of the complete gene sequence is well within our grasp and will be fundamental to the analysis of complex multifactorial traits, including all the major chronic human diseases. Genetic marker segregation among 'affected' individuals in a pedigree, however complex, can now be done by using the essentially unlimited collection of restriction fragment length DNA polymorphisms. This can, in principle, identify all the inherited components of any complex trait and, with a knowledge of the human gene sequence, identify their functional basis. Thus one can now envisage a complete genetic and functional analysis of all complex inherited traits, including the major chronic diseases, and normal variation in physical and behavioural attributes.