Glossary of Terms

  • Amniocentesis: A genetic procedure in pregnancy in which amniotic fluid is collected from the amniotic sac. Amniocentesis is performed between 14 and 18 weeks of pregnancy.


  • Autosomal Recessive Disorder: A disorder caused by mutations in both copies of the same gene. Mutations resulting in an autosomal recessive disorder are inherited from both parents who are carriers.


  • Carriers: Individuals who have a genetic mutation in one copy of a gene. One gene is normal and the other copy is abnormal. They do not have symptoms because they still have one working normal gene, which is sufficient to keep them healthy.


  • Chorionic Villus Sampling (CVS): A procedure in which a piece of tissue is collected from the placenta. CVS is usually performed between 10-14 weeks of pregnancy.


  • Chromosomes: There are 23 pairs of chromosomes, which contain the genes. The first 22 pairs are the autosomal chromosomes and are assigned numbers 1-22. The 23rd pair are called the sex chromosomes (X and Y) because they determine whether an individual is male (XY) or female (XX).


  • Genes: Units of genetic material (DNA) that are passed down from parents and determine how a body functions and develops.


  • Genetic Mutation: A change in DNA.


  • In-vitro Fertilization: Assisted reproductive technology in which an egg is fertilized outside a female's body.


  • Prenatal Diagnosis: Testing for the presence of a genetic condition, as well as other abnormalities, in the fetus during pregnancy.