Studies with Escherichia coli Sex Factors (original) (raw)

1. David Freifelder
2. Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts

Excerpt

Some strains of the bacterium, Escherichia coli, contain an extra-chromosomal, DNA-containing, genetic element known as a sex factor. A cell harboring such an element is called a male since it is capable of transferring genetic material to a second cell, a female, which lacks a sex factor. The simplest male-determining factor is called F (for fertility). Sometimes chromosomal genes are also present in the sex factor, in which case it is called an _F_′ (F-prime). Many F′ elements are known, of which a few examples are F′Lac (lactose), F′Gal (galactose), and F′Thy (thymidylate synthetase). There is one type of male in which the sex factor is not extra-chromosomal but is integrated into the chromosome. Such a male is called an Hfr. When Hfr cells mate with females, the chromosomal genes are transferred sequentially from a single point in the chromosomal map and F is transferred last. Normally, mating is interrupted...