Sex-Limited Traits
Sex Limited Traits are traits expressed only in one sex, although the genes controlling thcm arc prcscnt as wcll as transmitted to both thc sexes. Therefore, males and femalcs with thc bamc genotype, with rcspcct to a particular locus may have different phenotypes.
Sex-Limited Traits arc determined by autosomal genes, whose phenotypic expression is determined by the presence or absence of one of the sex hormones. Since sex hormones are the limiting factors, rhc phenotypic expression of these genes is limited to onc sex or the other. The most obvious exanlples are the secondary sex characteristics. Beard development in human beings is one such sex-limited character as men have beards, and woman normally do not. Yet studies indicate no significant differences between thc sexes in number of hairs per unit area of skin surface except in their development. This appears to clepend on sex hornlone production. Any disturbance in these hol-rnones in women rnay result in the development of beard. Similarly, the full development of breasts in females, and presencc of prostate glands in males are thc examples of sex-limited traits seen in human beings. Traits like egg laying in chickens, oviposition behaviour in insects are somc other such examples. Milk production in mammals is limited to females, but certain bulls are in great demand among dairy breeders and artificial inscinination associations because their mothers and daughters have incresed milk production records.