for BLAS students

this article is published in the seto pana magazine of HWHIC.
Pls go through this article


Nature’s balance

Raghubar Shrestha
Dept of Biology

In the early childhood, not many differences can be seen between male and female baby. In the society, it is realized that the female baby learns fast to speak. The female baby is slightly talkative in comparison to male baby.

Major differences set as they grow. As early as 8 or 9 years of age, in female child, the hormones come into play. The Follicle Stimulating Hormone FSH from the pituitary gland starts the developing of the female reproductive organ like the ovaries. The eggs develop inside the ovaries. The development of the eggs in the ovary is expressed by the onset of menstrual cycle. The developing egg also produces the hormone - Estrogen. This hormone has various effects on the body of girls. There is deposition of fat at different parts of body like thigh and hip. The mammary gland starts being developed. With these, they also develop little shyness. As they grow, they give attention towards the things which can make them pretty.

In case of male child, it is slightly late. Only at about the age of 12 or onward, the Follicle Stimulating Hormone from the pituitary gland starts developing the testis. The Leydig cells inside the testis produce the hormone called Testosterone. The testis starts the production of sperms. The hormone brings the changes like the different pattern of hair distribution in the body, the low pitched voice, and the muscular body. As boys enter puberty, they tend to exhibit more aggressive behaviour, and there is little doubt that the dramatic rise in male sex hormones surging through their blood is responsible for this change. For any hormone to influence behaviour, it must first reach the brain and affect it. Both male and female sex hormones (Testosterone and Estrogen) concentrate selectively in certain regions that play an important role in courtship, sex and mating behaviour and aggressive– behaviour in which the sexes differ most.

In 1973, it was demonstrated for the first time that male and female brains differ structurally in many ways. Castration of male monkeys shortly after birth produced the female hypothalamic pattern while injection of testosterone into female triggered the development of the male pattern. This was the first evidence that there were structural brain differences in the sexes that the sex hormones circulating before, at, or after birth could change the brain. Based on these and later observation, scientists concluded that the basic plan of the mammalian brain in female and stays that way unless “told to do other way” by masculinizing hormone. Females tend to have a longer left temporal lobe and the posterior portion of the corpus callosum is bulbous and wide, while in males the corpus callosum is generally cylindrical and fairly uniform in diameter. This may indicate that there are more communicating fibers between the hemispheres in females.

Both male and female children come up into adolescent with these changes. All these changes are developed to suit the reproduction later on. The effect of the hormones is that, unknowingly, they are being attracted towards the opposite sex. Puberty is the period of life, generally between ages of 10 and 15 years, when the reproductive organs grow to their adult size and become functional. These changes occur in response to rising levels of Gonadial hormones (Testosterone in male and Estrogen in female). It is important that puberty represent the earliest time that reproduction is possible. The eggs are developed earlier in the girls, but the whole body system is fully made ready for the reproduction at about the age of 20 only. Most women reach the peak of their reproductive abilities in their late 20s. After that ovarian function declines gradually, presumably because the ovaries become less and less responsive to gonadotropin signals. Estrogen production declines. Eventually the ovulation and menstruation cease. This normally occurs between the age of 46 and 54 years. This event is called menopause. This signifies that the female is no more capable of reproduction. But there is no equivalent of menopause in males. The male’s reproductive capability seems unending. Healthy men are able to become father of children well into their 80s. However there is noticeable difference in sperm motility with aging.

In the society, the marriage is a legal process to undergo reproduction. In the reproduction, the male partner has very short role. The husband donates the sperms for fertilization. Once the egg/s is/are fertilized, the fertilized egg/eggs are implanted in the uterus of the female or the wife. The fetus develops within the womb in about nine months. This gestation period is much challenging in the life of woman. After nearly nine months period, she gives birth to baby/babies either female or male. After nine month long period of very difficult situation, she can now breathe with peace. The act of giving birth to baby (parturition) is even more challenging and difficult. Parturition is the culmination of pregnancy. The series of events that expel the infant from the uterus are referred to collectively as labor. During this period, the mother may sacrifice herself. This act is much painful to the female but male partner is free from all these troublesome jobs.

After the birth of child, both partners look after the child, but it is mainly the responsibility of the mother to rear the young one/s. The Nature has given the main responsibility to the female counter part.

All these are due to the fact that the females have a pair of X chromosomes in the nucleus of the cells together with 22 pairs of Autosomes. Unlike, in the males, there is only one X chromosomes and one Y chromosome in addition to 22 pairs of chromosomes. The very thing here to notice is that the females are much safer as they have a pair of X chromosomes. It is a boon for the females as they do not generally develop the different types of genetic diseases like hemophilia, color blindness etc. In human beings, about fifty X chromosome linked defects have been reported up to now. The most important and common defects in man are :

1. Color or red - green blindness 2. Haemophilia
3. Anhidrotic ectoderma ( non functional sweet gland) 4. Night blindness
5. Myopia ( short sightedness) 6. Juvenile glaucoma
7. White fore lock etc.
Hemophilia is most serious and notorious disease which is more common in man than in woman. It is also known as Bleeder’s disease. The person which contains recessive gene for hemophilia lacks in normal clotting substance in blood. So, normal and minor injuries cause continuous bleeding and ultimate death due to the hemorrhages. This hereditary disease was first reported by John Cotto of Philadelphia in 1803 in man. This disease has been most common in Royal families of Russia and England. Queen Victoria and her further generation were having hemophilic disease. The males are easily victimized to these diseases because of only one X chromosome. The defects in the X chromosome are frequently expressed in males. When one of the X chromosomes is defective, the women are not affected by any deadly disease as it is dominated by another X chromosome. The women in this condition is said to be carrier of the defective X chromosome. They can transmit the defective X chromosome to daughters and sons. However the sons are easily affected by it. Knowing the fact that the daughters transmit the recessive genes to their sons, the Royal families in those days got their daughters married in other countries.

The daughters are affected by such deadly diseases only when both of the X chromosomes are defective. It is possible only when there is marriage between the diseased man and woman or diseased man and carrier woman. Generally diseased men and women do not get married easily. In case of the marriage between diseased man and carrier woman, only half of the daughters will get both defective X chromosomes and other half will get one defective X chromosome. When there is only one defective X chromosome, these daughters are not affected, they will just become carrier of defective X chromosome and transmit it to sons.

There are certain other cases which are linked to the Y chromosome. The Y chromosome is only present in males. So these Y chromosome linked defects are directly transmitted from father to son. One of the simple examples of this can be taken as ichthyosis hystrix gravis hypertrichosis (excessive development of hairs on pinna or ear). Still others are both X-Y linked. In human beings, several diseases are X-Y linked such as total colour blindness, skin diseases (Xeroderma pigmentosum and Epipermolysis bullosa), Retinitis pigmentosa, Spastic paraplegia etc. From all these, it is now clear that the females are much safer from all these notorious and deadly inheritable genetic diseases.

At the end, it can be said that the Nature is looking both the males and females equally without any discrimination. Any one of the males and females is not important for the Nature. Both are needed and both can contribute to the continuity of the race. Both should go together for the betterment of the race.