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.