In this article we will discuss about the genetic map of E.coli.
Several methods have revealed that the genetic map of the main chromosome of E. coli is an un-branched circle with a circumference of 100 minutes (Fig. 17.5) which corresponds to the transfer time during conjugation. About 650 genes have been mapped. Some important features of the genetic map have been noted. In many cases functionally related genes occur together and form clusters.
For example the genes involved in the catabolism of lactose and synthesis of amino acids tryptophan and histidine are all clustered together. On the contrary, some functionally related genes are placed far apart.
For example, the genes related with catabolism of arabinose are present at three sites, and those concerned with biosynthesis of leucine occur at several different sites. The orientation of all genes is not the same. Genes are arranged in both clockwise and anticlockwise manner.