Mitosis is a kind of cell division that produces 2 daughter cells that are genetically identical to both the other daughter cell and the parent cell. It is a process of exact duplication of the genetic material (chromosomes) in the parent cell, then dividing, each with the same original number and sequence of chromosome.
It is used for growth and development because they're the process of where the number of cells increases, and how? By mitosis. These new cells must be exactly identical to the other originally existing cells, as for example you wouldn't suddenly grow some skin cells as a replacement of nerve cells. Mitosis of nerve cells produces the same type of nerve cells, mitosis of skin cells produces skin cells.
Well sickle cell disease requires two homozygous recessive alleles so you would have the disease but if your'e heterozygous you have the sickle cell trait.
