SEX DETERMINATION IN HUMAN

There are two types chromosomes in an individual i.e. sex chromosomes and autosomes. Sex chromosomes are responsible sex determination of the individual in dioecious or unisexual organisms. The normal chromosomes, other than sex chromosomes of an individual are known as autosomes. Sex chromosomes mat be similar in one sex and dissimilar in the other. The two conditions respectively called homomorphic (Similar, i.e. XX, ZZ) and heteromorphic (Dissimilar i.e. XY, ZW). Individuals having homomorphic sex chromosomes produce only one type of gametes. They are therefore, called homogametic (e.g. human female, male birds and Drosophila female). Individuals having heteromorphic sex chromosomes are called heterogametic and produce two types of gametes (e.g. human male, female bird and normal Drosophila male).

In human being, sex is determined by the chromosomal mechanism of sex determination. According to this mechanism, there are certain chromosomes called sex chromosomes or heterosomes or idiochromosome, which are responsible for sex determination. It is called XX-XY type of sex determination. In human being, the female possess two homomorphic (isomorphic) sex chromosomes i.e. XX. Yhe male possess two heteromorphic sex chromosomes i.e. XY. The Y-chromosome is often shorter and heterochromatic (made up of heterochromatin). Despite differences in morphology, the Y-chromosome pairs with X-chromosome at a certain segment during meiosis. It therefore, carries a segment which is homologous with a segment of X-chromosome. The remaining segment of Y-chromosome is non-homologous and carries only Y-chromosome linked or holandric genes, e.g. Testis Determining Factor.

Human beings have 22 pairs of autosomes and one pair of sex chromosomes. All the ova (haploid sex cells i.e. egg) formed by females are similar in their chromosome type (22+X). Therefore. Human females are homogametic in nature. The male gametes or sperms (haploid sex cells) produded by human males are of two types i.e. (22+X) and (22+Y). Human males are therefore heterogametic in nature. The two sexes produced in the progeny (baby) may have 50:50 ratio. This type of sex determination was reported in a plant Sphaerocarpus for the first time and is also found plants like Melandrium and Coccinia.

It is therefore, biologically proved that human males are responsible for the sex of the baby born to him and not the female. The myth that people believe, “a mother is responsible for the sex of the baby” is totally wrong. In many countries including India, females are punished and treated badly for giving birth to girl child due to lack of sex education. Sex education is the demand of time to have a healthy and balanced society. Neither male nor female is responsible for the sex of the baby. It is a random process. If the sperm carrying X-chromosome fertilize the egg then the baby will be a girl and if the sperm carrying Y-chromosome fertilize the egg then the baby will be a boy. If, someone is to be blamed then its father, for the sex of the baby but I have already mentioned earlier that nobody can be blamed for this because it is a random process and can’t be controlled by anything.

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