Principles of Biochemistry, Volume 3 - A. Lehninger 1985

Molecular Mechanisms of Genetic Information Transfer
DNA: Structure of Chromosomes and Genes
A large number of genes are concentrated in a single chromosome

How many genes are contained in a single chromosome? We can provide an approximate answer to this question in the case of E. coli. It is estimated that the single chromosome of E. coli contains more than 3,000 genes, and possibly as many as 5,000. An attempt was made to directly count all the Polypeptides present in E. coli after separating them by two-dimensional Electrophoresis. About 1,100 spots corresponding to individual polypeptide chains were detected on the electropherograms (Fig. 27-25). However, this number is a minimum, since this method does not resolve all polypeptides and lacks sufficient sensitivity to detect the presence of Proteins represented in The Cell by only a few molecules.

Using various genetic approaches, the mapping order of many genes on viral and bacterial Chromosomes has been established. The partial Genetic Map of E. coli shown in Fig. 27-26 illustrates the relative positions of some of its genes within the circular DNA molecule.



Last update: 06/08/2026

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