The human body is comprised of millions of cells. Inside each cell are genes which control our physical characteristics and our development. Each person receives two copies of genes. One from mother and the second from the father. So, the children receive half of their genetic makeup from each parent. This does not mean, however that they are simply combination of their parent’s traits. This is because of the complex interaction between the genes as well as its interaction with the environment. While most of the characteristics and conditions have a complex genetic and environment basis, there are a few traits and diseases for which the role of genes is more important and more understood. So it is not just one parent’s gene solely responsible for disabilities.