All in all, cell division is a complex process in which the mechanisms involved in copying and recombination are responsible for variations in DNA. It is these (sometimes small and sometimes larger) variations in our DNA that make each one of us unique. Sometimes they result in 'errors' and these may form the basis for specific disorders.
Some differences or abnormalities in our chromosomes or genes come to us via our parents' reproductive cells. In other words the variation is present in the egg and/or sperm cell and is therefore transferred to all our cells. As an embryo we develop from these two parental reproductive cells (the egg cell and sperm cell), which multiply after merging (fertilization) through cell division and specialise further to form a new organism. That is the basis of our inheritance: it explains why we resemble our parents and other family members - because each family has its own specific genetic variations - and also why we sometimes inherit specific disorders. We describe these disorders and diseases as congenital or inherited disorders.<top>
You can read more about this under Inheritance.