Flaws in Developmen of Human

The human growth and development in spite of its complexity works perfectly most of the time. But while development goes awry it creates a giant or dwarf, a child along with multiple fingers or toes an albino or haemophilic or even worse than these. All birth defects are loosely grouped like 'congenital defects'. Causes for birth defects can be sought in three general areas; defective genes, abnormal arrangements of chromosomes and not favorable factors occurring in the uterine environment throughout pregnancy. The list of hereditary birth defects is long and in some cases the particular chemical defects because of defective genes is known, for instance, Haemophilia, sickle cell, thalassemia, anaemia and phenylketonuria. But not all genetic defects are inherited. In a number of embryos the genetic instructions that govern growth are primarily correct but somewhere during cell divisions the instructions become garbled and mishaps of this son generally involve not a single defective gene but a complete rearrangement, of the cell's genetic material. Down's syndrome is one such example.