monosomiassa

Monosomia is a type of aneuploidy, which is an abnormal number of chromosomes. In monosomia, an individual is missing one chromosome from a homologous pair. Normally, humans have 23 pairs of chromosomes, totaling 46 chromosomes. If an individual has monosomia, they will have 45 chromosomes instead of 46. This condition can occur in any of the autosomes (non-sex chromosomes) or sex chromosomes.

Monosomia is usually caused by a nondisjunction event during meiosis, the process of cell division that produces gametes (sperm and egg cells). Nondisjunction occurs when homologous chromosomes fail to separate properly, or when sister chromatids fail to separate. This results in a gamete with an incorrect number of chromosomes. If this abnormal gamete is involved in fertilization, the resulting zygote will have an unbalanced chromosomal complement.

The consequences of monosomia depend on which chromosome is affected. Monosomies involving autosomes are generally not survivable and often result in early embryonic or fetal loss. The most well-known example of monosomy in humans is Turner syndrome, which affects females and is characterized by the absence of one X chromosome (45,X). Individuals with Turner syndrome may have a range of physical characteristics and health issues, including short stature, infertility, and heart defects. Monosomies of other chromosomes, such as monosomy 21 or monosomy 18, are not compatible with life beyond the fetal stage.