WOMEN’S BODIES: SEX AND REPRODUCTION

MARCH 11TH, 2009
By ADMIN

Reproduction is, to me, the most wonderful, fascinating, awesome aspect of life. There is just so much to marvel about, whether it is the multiplication of viruses, the germination of plant seeds, a bird pecking its way out of an egg or the birth of a baby animal. The more we discover about reproduction, the more miraculous, and mysterious and intriguing it becomes.

Reproduction in humans, as in most other animals and plants, involves sex. I don’t mean sexual intercourse (though that is part of it) but the existence within the species of females and males with separate roles in the reproductive process.

The essential feature of sexual reproduction is that each new individual receives an equal share of genes from a female and male of the species. Half the genes are carried in the female gamete -the ovum – and the other half in the male gamete – the spermatozoon. Male and female gametes unite to form a zygote from which the new individual develops. Sex ensures that in every new

generation each individual has a unique set of genes contributed by a male and female parent.

Genes and sex

Genes are the basic units of inheritance in all living things. They carry information

that dictates all the characteristics of an individual such as species, sex, colouring shape, pattern of fingerprints and so on, Genes make up the threadlike structures known as chromosomes, which are found in 23 pairs in the nucleus of every human cell except the ovum and sperm; Sperm and ovum contain only one сchromosome of each pair. The arrangement of genes is called the genetic code, and is different for each individual except in the case of identical twins.

Our sex is determined by our genes from the moment of conception. The sex genes are known as X and Y. An ovum always contains the X gene: the sperm contain X or Y. When an ovum and sperm unite to create a new individual, the combination XX will result in a female foetus; XY in a male. Thus sex is determined the genetic contribution of the sperm.

Because the biological purpose of sex is reproduction, the XX combination equips the female with the reproductive org she will need for conception, pregnancy birth and the early nourishment of offspring, while XY genes equip the m^:with the means of producing sperm introducing them into the female body.

The influence of the XX or XY geneticcombination on the development of reproductive system becomes apparent early in the life of the embryo. Special organs called gonads are needed for sexual reproduction. The female gonad is the ovary and the male gonad is the testis. XX genes lead to the development of ovaries in female embryos, and the Y gene is responsible for the development of testes in males. Gonads contain two distinct tissues: germ cells that will develop into gametes (ova and spermatozoa) and stromal cells that support the germ cells and produce the hormones needed for the female and male roles in reproduction.