pediatrics
Overview of Chromosomal Abnormalities
Terminology
Some specific terms from the field of genetics are important for describing chromosomal abnormalities: Aneuploidy: The most common chromosomal abnormality caused by an extra or missing chromosome. Karyotype: The full set of chromosomes in a person's cells. Genotype: The genetic constitution determined by the karyotype. Phenotype: The person's clinical findings including outward appearance—the biochemical, physiologic, and physical makeup as determined by the genotype and environmental factors (see Overview of Genetics ). Mosaicism : The presence of ≥ 2 cell lines differing in genotype in a person who has developed from a single fertilized egg. 