Localization of genes on human chromosomes

The genetic machinery of cells controls the biological functions such as food uptake, biosynthesis and reproduction. External characteristics and complex patterns of behaviour at the level of the organism are also programmed in the genetic material. The mechanisms of expression of the genes and the regulation of expression have been studied extensively in micro-organisms. These studies have revealed information about the position of genes on the chromosomes of these cells and about their function in cell metabolism. The techniques available for the formation of new combinations of genetic information such as fusion of cells (conjugation), transfer of genes by isolated DNA (DNA-transformation) and transfer by viruses (transduction) have facilitated the genetic studies. The investigation of gene expression in multicellular organisms including man has been hampered by the absence of techniques which could provide genetic recombination. New recombinations are produced in nature by sexual reproduction. Therefore, for many years, the formation of gametes and the recombinations between chromosomes, which occur during meiosis, have provided the basis for the study of the genome of higher organisms including man.