Phenotypic sex

The fetal testis induces a male type of phenotypic sex development by virtue of producing two sorts of hormones. The first of these is the androgen testosterone, which triggers the formation of male structures from the Wolffian duct, the urogenital sinus, and the external genital primordia, via mechanisms considered below. The second type of fetal testicular hormone is a macromolecule, apparently a glycoprotein, that evokes involution of the Mullerian duct during normal male sex differentiation. 

Phenotypic sex differentiation is determined by hormonal products of the gonads. Anomalous hormone production during fetal development frequently results in ambiguous genitalia. 

Testosterone, the principal male sex steroid hormone, is synthesized in five steps from cholesterol, as shown below. In the last step, five isozymes catalyze the 17/3-hydroxysteroid dehydrogenase reactions that interconvert 4-androstenedione and testosterone. Defects in the synthesis or action of testosterone can impair the development of the male phenotype during embryogenesis and cause the disorders of human sexuality termed male pseudohermaphroditism. Specifically, mutations in isozyme 3 of the 17/3-hydroxysteroid dehydrogenase in the fetal testis impair the for-... 

Analysis of ERa-deficient mice showed that both sexes are infertile and display a variety of phenotypic changes associated with the gonads, mammary glands, reproductive tracts, and skeletal tissues. In addition,... 

Ethylene is the major feminizing hormone in most cucurbits showing a wide range of sex phenotypes with some exception of watermelon in which a steady increase in ACS isozymes transcript level in male flowers compared with female flowers has been reported. ... 

Males and females of the North American slimy salamander Pkthodon glutinosus prefer substrates previously occupied by a conspecific over their own, but they do not discriminate between the sexes. However, in an olfactometer with live salamanders as odor source, male and female P. glutinosus, male Fkthodonjordani, and a related phenotype ( species A ) all preferred female over male odors. Male P. glutinosus and species A chose conspecific over heterospecific female odors in the olfactometer. This indicates that airborne odors may constitute an important pre-mating isolation mechanism (Dawley, 1984). 

Mice (see Notes 1 and 2) any variety of mice can be used. Pathogen-free CD1 and NMRI mice from either sex have also been commonly used. As mentioned above, we recommend the use of inbred mouse strains since they are genetically well defined and uniform providing the advantage of high reproducibility not available with standard outbred mouse strains. In addition, due to the phenotypic uniformity of an inbred mouse strain, the sample size can be smaller than when using outbred stocks. 

Tompkins L. and McRobert S. P. (1995) Behavioral and pheromonal phenotypes associated with expression of loss-of-function mutations in the Sex-lethal gene of Drosophila melanogaster. J. Neurogenet. 9, 219-226. 

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