Some diseases pass on from one generation to the next, i.e. from parents to their children. Heredity describes how parents pass on their characteristics to their children. Sometimes it is a tendency towards a certain illness. These diseases are known as hereditary or genetic diseases because they are traceable to the genes of the parents. Do you know which diseases are hereditary diseases?
As we know that the sex of a child depends on the respective number of chromosomes X and Y obtained from the parents. There are some other genes connected to sex, called the sex-linked genes. The chromosomes in the cells of a new born baby are a mixture of its parent’s genes.
Colour blindness is one of the sex-linked diseases. The incidence of this disease is more in males than in females.
Haemophilia, a rare disease in which blood does not clot or clot very slowly, is another sex-linked disease. This is due to X-chromosomes which are carried by females only. This disease is inherited by male children only from their mother.
Albinism is another inherited disease in which a person lacks in melanin, a dark pigment which gives colour to the skin, hair and eyes. The persons suffering from this disease have pinkish skin, greyish hair and are very sensitive to light.
The chances of a child to suffer from diabetes and cancer are more if the parents suffer from these diseases. Sickle cell anaemia, a physical disorder in which blood cells are formed irregularly like a sickle in shape, is also inherited from parents. This disease produces abnormal haemoglobin with sickle blood cells.
There are some diseases which are produced due to some disorder in chromosomes. Some children have small flat face, small fingers, weak muscles and squint eyes. Their lifespan is short, just 20 to 30 years and mental development is not more than that of a four years old child. This is due to the presence of 47 chromosomes instead of 46, and their abnormal combination. In medical terminology this disease is called Monogolism or Down’s syndrome after the name of the doctor John Down, who studied it.