Scientists currently estimate that over 10,000 of human diseases are known to be monogenic.Pure genetic diseases are caused by a single error in a single gene in the human DNA.
X linked diseases are monogenic disorders that are linked to defective genes on the X chromosome which is the sex chromosome.
The X linked alleles can also be dominant or recessive.
The global prevalence of all single gene diseases at birth is approximately 10/1000.
In Canada, it has been estimated that taken together, monogenic diseases may account for upto 40% of the work of hospital based paediatric practice (Scriver, 1995).
The severity of the disease depends on the mutations involved in the genes, and their interplay.
A haemoglobin molecule has sub-units commonly referred to as alpha and beta.
Individuals can also be tested for thalassaemia through routine blood counts.
Thalassaemic patients may have reduced fertility or even infertility.
After haemoglobin molecules give up their oxygen, some may cluster together and form long, rod-like structures which become stiff and assume sickle shape.
Unlike healthy red blood cells, which are usually smooth and donut-shaped, sickled red blood cells cannot squeeze through small blood vessels.
Early treatment of thalessaemia has proved to be very effective in improving the quality of life of patients.