-A graduate student from the United Arab Emirates
August 19, 2015
In most cases yes. And the way it is often done is to select only girl embryos.
To do PGD, scientists take eggs from the mother and sperm from the father and do something called in vitro fertilization, or IVF (click here to learn about IVF). During IVF, the father’s sperm will fertilize the mother’s eggs outside of the body and make lots of embryos.
One of the 23 pairs of chromosomes, the X/Y, determines a person’s sex. These are called sex chromosomes.
Females have two X chromosomes (XX) and males have one X and one Y chromosome (XY). Mutations in the X (and to a lesser extent the Y) can lead to X-linked or sex-linked diseases.
Sex-linked diseases are one of the most common kinds of genetic disorders. They are special because they can be much more common in males than females, or vice versa, depending on the disease.
Diseases Caused by Extra or Missing Chromosomes
While we usually have two copies of 23 chromosomes, this is not an absolute rule. Sometimes, embryos have just one copy or three copies of a chromosome instead of two.
Having one copy is called monosomy and having three is called a trisomy (click here to learn more about trisomies like Down’s Syndrome). Some scientists estimate that a few percent of pregnancies are like this but most of the embryos don’t survive to birth because extra or missing chromosomes are usually fatal.