GENES AND INHERITED DISEASES
Charles H.Barrow once commented ‘a man’s total life span is programmed in his genes: that somewhere imprinted in our internal computer cards are time tables for everything from first teeth to diabetes or old age…’It was Johan Gregor Mendel who in the course of his experiments with Pea plants in the 1860’s hit upon the concept of heredity. He discovered that the transmission of certain characteristics passed through successive generations. This was also confirmed by Thomas Hunt Morgan while researching with fruit flies during the 1930’s. Though Mendel had studied about plants and Morgan that of insects their findings are applicable to all life forms because genes form the basic unit which controls development.
In the case of all organisms, both parents contribute to the heredity of the offspring. So in the case of a human being each parent contributes to the physical trait. Though each contributes equally, one gene may outweigh the other. For example if a parent has a blue eye and another brown the child may be born brown eyed. In this case the brown eyed gene is called ‘Dominant Gene’ and the other ‘Recessive Gene’. The recessive gene may however express it itself in the next generation displaying blue eyes in the new generation offspring.
This implies that just as physical traits are inherited, some of the diseases too may get transmitted from one generation to the other. The human chromosome which is sum total of human genes is what distinguishes different species. There are 46 chromosomes in a normal human body or in other words 23 pairs. With one of the each pair inherited from each parent, 44 chromosomes are called ‘Autosomes’ which is responsible for the general characteristics of the body and they are the same in both the men and the women. The remaining two are called ‘Sex chromosomes’ usually identified as ‘X’ or ‘Y’. It is this characteristic which distinguishes the male from the female. Most inherited diseases could be on account of abnormality in autosomes and those of sex chromosomes.
Some of the noteworthy diseases due to defective Autosomes are as follows:
· DOWNS SYNDROME: This is also called ‘Mongolism’. The usual physical indications of this are short thick hands and feet, short fingers and severe mental retardation. There could also be peculiar palm prints and heart defects.
· STURGE-WEBERS SYNDROME: Symptoms are usually muscles without tension, enlarged liver and heart defects accompanied by mental retardation.
· EDWARDS SYNDROME: Physical indications are low set ears and eyes, deformities of the hip, kidney malformations and heart defects. As in earlier cases the person would be mentally retarded.
· PATAU’S SYNDROME: The physical indications are defects of skull, eyes, mouth, hands, skin, abdomen, kidney, heart and sexual organs. Such a person would be mentally retarded too.
· LEWIS SYNDROME: Symptoms of this are poorly developed gonads, loss of bone density, early onset of senility and mental retardation.
· STADLER-PFEIFLERS SYNDROME: Usually people afflicted by this would have deformed fingers genital abnormality and mental retardation.
· ORO-FACIAL DIGITAL SYNDROME: Such a person apart from displaying mental retardation would have a forked tongue, defective upper lip and mouth.
SEX CHROMOSOME DISORDERS
Some of the disorders afflicting women are:
· TURNERS SYNDROME: Physical characteristics of people afflicted by this are stunted growth, webbed neck, shield-shaped chest and degeneration of ovaries. The possibility of color blindness is also very high.
· TRIPLE SYNDROME: The usual symptoms are scanty and irregular menses with a mild mental retardation.
· TETRA X SYNDROME: The females afflicted by this have normal sexual development but are mentally retarded.
· PENTA X SYNDROME: People afflicted by this have severe nervous and arterial disorders.
Some of the disorders afflicting men are:
· PSEUDO-HERMATHRODITISM: Men afflicted by this have gonads of one sex but with external sex organs deviating to the opposite sex.
· KLINE FELTERS SYNDROME (Type 1): Men afflicted by this are usually sterile with testicular atrophy and could also be mentally retarded.
· KLINE FELTERS SYNDROME (Type 2): Such men would be tall with long arms and legs and have small sex organs. They would be having a very low IQ and also very aggressive.
· TETRA X-Y SYNDROME: Such men have both skeletal and sexual anomalies and would be severely retarded.
Some disorders affecting both men and women are:
· MOSAICISM: People afflicted by this have some chromosomes that are normal and some that are abnormal.
· MARFAN’S SYNDROME: People afflicted by this have long fingers, loose ligaments, muscles without tension and dislocation of lenses.
These are genetic disorders some of which are not curable. But with the rapid growth of genetic engineering, some cure may be insight during the not too distant future.