In this article the major genetic disorders and the modes of their transmission is discussed. We have also briefly mentioned the modalities by which many of the genetic diseases can be detected before birth. The genetic counselling is helpful in many ways in order to advise the parents for keeping the fetus or terminating the pregnancy. The physician can reduce the anxiety of the parents, but the main decision has to be made by the parents themselves. The most beneficial genetic 
cou􀀲selling is before pregnancy to determine whether a couple should have a baby or not. There is no definite indication for amniocentesis unless there is a definite evidence of a dreadful disease in the fetus. The appli­cation of many of the diagnostic modalities of course, depends largely on the moral, religious and social situations, which differ in each case.