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Genetic Disorders
There are many diseases whose roots can be traced to the genetic make-up of the human beings. A majority of the genetic conditions and the resultant disorders are inherited from the parents.
But there are several other problems that occur due to sudden inexplicable mutation or gene change when the child is in embryonic stage. One such problem is Down syndrome that causes heart problems, poor muscle strength and flat face, etc.
Broadly speaking genetic disorders are categorized by the way they occur.
1. Autosomal dominant disorder (ADD): If the problem has been transmitted from the genes of only one parent, it is called autosomal dominant disorder. Children of such parents have 50% chance of inheriting this disorder. Examples of ADDs are:
- Huntington’s disorder: It is characterised by a gradual increase in involuntary, rapid, jerky motions and mental debilitation. It usually affects people between the ages of 30 and 50.
- Marfan’s syndrome: The characteristics of the disorder include long, thin arms, legs and fingers. Patients suffering from Marfan’s syndrome generally have stooping shoulders and bluish eyeballs. Most of these people also suffer from heart and eye problems. It is believed that Abraham Lincoln suffered from Marfan’s syndrome.
2. Autosomal recessive disorder (RGD): It is transmitted by the genes of both the parents.
Around 25% children born of such parents inherit this disorder. It is also believed that this malady generally affects people of certain ethnic communities rather than all the population. Two important diseases caused by recessive disorder are:
- Sickle-cell anaemia: It generally affects the world’s black and Hispanic populations. The patients have sickle-shaped red blood cells and people afflicted by the disorder don’t usually survive beyond the age of 30.
- The Tay-Sachs disorder: This gene is found in one out thirty Ashkenazi Jews. This disorder leads to blindness and death before the age of four. The symptoms of this disorder appear 5 months after the birth.
3. Sex-linked genetic disorders (XLGDs): They are caused by X (female) and Y (male) chromosomes. This disorder is characterised by
Color Blindness: Color blindness means inability to differentiate between the colors such as green and red. The gene is usually carried by X chromosome, which is transmitted by the mother.
Haemophilia: It is characterized by the absence of protein, which is responsible for the clotting of the blood. People suffering from this disorder are prone to die of bleeding even from simple cuts and injuries. Haemophilia A is the most lethal form of this disease. English royalty is known to suffer from this disorder.
4. Multifactorial genetic disorders (MFGDs): Some genes develop due to environmental factors. It means that they are present outside the organism itself. This disorder is characterized by problems of diet and metabolism, which can lead to obesity, diabetes, alcoholism, high blood pressure, rickets and infectious diseases such as measles, scarlet fever and TB.
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