Genetics, Chromosome Abnormalities

Genetic disorders traditionally fall into three main categories: single-gene defects, , and multifactorial conditions. A chromosomal abnormality, or chromosomal aberration, is a disorder characterized by a morphological or numerical alteration in single or multiple chromosomes, affecting autosomes, sex chromosomes, or both. The normal human karyotype contains approximately two meters of DNA organized into 46 chromosomes: 22 pairs of homologous autosomal chromosomes and a set of sex chromosomes that compromise two X chromosomes in females or an X and a Y chromosome in males. All the genetic necessary for growth and development derive from chromosomes (around 20 to 25 thousand genes). Chromosome abnormalities usually involve an error in cell division (mitosis or meiosis), which may occur in the prenatal, postnatal, or preimplantation periods. These alterations have significant clinical consequences, i.e., spontaneous abortions, stillbirths, neonatal death/hospitalization, malformations, intellectual disability, or an identifiable syndrome. Accurate identification of these chromosomal errors is essential for prevention strategies, genetic counseling, and appropriate treatment.