If a fertilized egg receives an X chromosome from the mother and an X chromosome from the father, the pregnancy will become a female. If the sperm carries a Y chromosome instead, the pregnancy will become a male. Since each of us receives one set of chromosomes from our mother and one set from our father, any abnormal gene received is generally counterbalanced by a healthy gene from the other side. We estimate that each individual carries 10 to 20 abnormal genes which, if they were in a pair, would cause that individual to have a particular genetic disease . People who carry a single genetic abnormality are called carriers and are generally healthy because they have one healthy gene to counterbalance .
Genetic diseases can also arise from an abnormal number or arrangement of chromosomes .
If the sperm or egg carries an extra chromosome, or is missing a chromosome, either a miscarriage or an abnormal pregnancy can result. Our ability to identify chromosome abnormalities allows us to provide patients with an increasing array of information to develop more productive treatment plans.