Finalization of sex at the time of fertilization is known as sex determination. All sex linked character show criss-cross inheritance and firstly it was studied and discovered by TH Morgan $(1910).$ Sex related trait may be divided into three types

$(i)$ Sex Linked Traits They are those traits the determining genes of which are found on the sex chromosomes. All the sex-linked traits present on a sex chromosome are inherited together

$(ii)$ Sex Limited Traits They are autosomal traits which are expressed in a particular sex in response to sex hormones although their genes also occur in the other sex, $e.g.,$ milk secretion in mammalian females, pattern baldness in males. The gene for baldness behaves as an autosomal dominant in males and autosomal recessive in females

$(iii)$ Sex Influenced Traits The traits are not due to particular genes but are by products of sex hormones, $e.g.,$ low pitched voice, beard moustaches. In males, pattern baldness is related to both autosomal genes as well as excessive secretion of testosterone