#clinical genetics

• Agenesis — The congenital absence of an organ, tissue, or body part, caused by the failure of its development during embryonic life. Unlike aplasia, where the embryonic bud exists but fails to fully mature, in this severe structural anomaly the initial blueprint of the organ is completely missing from the genetic profile.
• Aneuploidy — A numerical genetic anomaly consisting of a change in the normal number of chromosomes within a cell or organism, through the loss or gain of one or more chromosomes from the basic diploid set. This structural phenomenon usually occurs as a result of chromosome nondisjunction during meiosis or mitosis and represents a major cause of severe phenotypic developmental disorders and spontaneous abortions.