Sex Linked, Sex Influenced and Sex Limited Traits

Content
Sex Linked, Sex Influenced and Sex Limited Traits
Sex linked traits 
Sex linkage in Drosophila
Sex linked lethals in Drosophila
Sex linkage in human beings
Sex linkage in poultry
Non-disjunction of sex chromosomes in Drosophila
Sex Influenced Traits (horned character in sheep)
Sex Limited Traits (cock feathering in poultry and baldness in man).
In earlier sections, while discussing the laws of inheritance, it was realized that reciprocal crosses would give same results. In other words, it did not make any difference, whether a particular character was present in male parent or in female parent. For instance, in pea when tall plants are crossed with dwarf plants, always tall plants are obtained in F] generation, irrespective of whether tall plants are used as male or as female parent. This would always bethe situation in bisexual plants or in hermaphrodite animals. However, in dioecious individuals, there can be two kinds of characters, namely : (i) characters which do not show any differences in reciprocal crosses (♀A x ♂B; ♀B x ♂A), and (ii) characters which show a difference in reciprocal crosses. The former type of characters are located on autosomes and the latter are either located on specialized chromosomes known as sex chromosomes or if located on autosomes, are influenced by or depend on sex of the individual, which carries it. Traits, which are carried on sex chromosomes are known as sex linked traits. Other characters whose expression in a particular genotype depends on whether the individual is male or, female, are known as sex influenced traits. Still another class of traits called sex limited traits are distinguished by the fact that one form of this trait may be expressed in one sex only and not in the other. These different types of traits related with sex will be discussed in this section.