DPevlopment of accessory sex Organs (phenotype), factors determiniting Development of psychologic al sex. 4 lnter telationship between brain and sex d

termining. DPevlopment of accessory sex Organs (phenotype), factors determiniting Development of psychologic al sex. 4 lnter telationship between brain and sex dfferentiation: Psychology and behavior (ii) Secretion of gonadotropins Interodüction Mankind is divided into two sexes, the males and the females What are the critena by which this classification is made ? There are four criteria, vizz. (i) the Chromosomal (or genetic) sex, (ii)the gonadal sex, (iii) the phenotype sex, and (iv) the Psychologica sex (i) if the chromosomal pattem is XX. then the subject, no matter what is the outward appearance, is genetically a female Conversely if chromsomal pattern is xy. the subject is male (irrespective of the ouier apptarance) Hence XX and xy are female and male genotypes respectively (ii) Testes and ovaries are the mäle and the female gonads respectrvely Therefore, when testes are present, the subjecl is, gonadally, a male Similarly, presence of the ovanes means that the subject is gonadally, a female (iii) By the acceesory sex organs (penis, epididymis, vas, seminal vesicales and the prostate in the male and Fallopian tube. Uterus, vagina and vulva in the temale) gender sex or the sex phenotype is deterrmined Thus famale phenotype will have female accessory sex organs and the male phenotype will have male accessoryt sex organs (iv) Psychological sex is the sex wnich the individual believes that he or she belongs Thus, if a qirl from her infancy, is mistaken as a boy and is reared up among the boys and she thinks that she is a boy, her psychological sex is male In vast majority of cases, there is no confusion in sex charactenstics, thai is, in a male, the genetic, gonadal. phenotype and the psychological sex are all male, so is the case with the females.Rarely however, anomalous situation anses Thus, someone may have a male genotype pattern of sex (XY) and yet the appearance from outwards (the external genitalia. the dress) may be of the femele type and the subjact believes that he is female. Two terms are commonly used - (i) sex determination and (ii) sex differentiation By the term sex detrmination. it is meant how the genetc sex pattems are made. Sex differentiation means the developement of gonads, accessory sex Organs and the Psychological aspects öf sex Thus, sex determination occurs durring the fertilization of the ovum. On the of her hand, in the early weeks of intrauterine life. the gonadal and gender sex of the fetus are not differentiated. After a few weeks of intrauterine life, a fetal gonadal and gender sex differentiation (that is, outward sex differentiating features like the development of testes, penis. prostate etc, in males or ovary, uterus, vagina. vulva etc in the female) occur. Mechanism of sex determination Human beings have 46 (23 pairs of) Chromosomes of which 44 are autosomes, and the rest two are sex chromosomes. These two sex chromosomes. in rase of the female, - are XX, whereas in case of male, ars XY. Therefore. the_ male and the female chromosomal pattern can be written as 44 + XY (=46_) and 44 + XX (=46) respctivel Owing to the reduction cell division (meiosis), a gamet (a spermatozoon or an unfertilized ovum) will contain 22 autosomes + 1 sex chromosome (i. e, total 23) In case of an ovum it has to be (obviously) always 22 + X, but In the case of a spermatozoon it may be 22 + X or 22+Y. Now, during fertilization. one such spermatozoon and one such ovum unite to form a zygote. Therefore from the ovum the_ zygote is always getting 22 +X, but from the spermatozoon it may get either 22 + X or 22 + Y. When fertilization occurs. therefore. the zygote's chrom, osomal pattren (Karyotype) can be 44 +, XX, or 44 + XY and the genotype or the genetic sex of the