monosominen

Monosominen is a term used in genetics to describe a chromosomal abnormality where an individual has only one copy of a particular chromosome instead of the usual two. This condition is a type of aneuploidy, which refers to an abnormal number of chromosomes. Monosomy typically arises due to errors during meiosis, the process of cell division that produces gametes (sperm and egg cells). If homologous chromosomes fail to separate properly during meiosis I, or sister chromatids fail to separate during meiosis II, a gamete can end up with one less chromosome than normal. When this abnormal gamete participates in fertilization, the resulting zygote will be monosomic for that chromosome.

The effects of monosomy vary greatly depending on which chromosome is affected and the extent of genetic material lost. Complete monosomy for an autosome (any chromosome other than a sex chromosome) is usually not viable and leads to embryonic or fetal death. This is because the single copy of the chromosome often cannot provide enough gene products to sustain development. However, partial monosomy, where only a segment of a chromosome is missing, can be survivable and may result in a range of developmental abnormalities.

Monosomy of sex chromosomes is more common and often survivable. For example, Turner syndrome, characterized by 45,X, is a form of monosomy where an individual has only one X chromosome instead of the usual XX or XY. Individuals with Turner syndrome typically have distinctive physical features and may experience a variety of health issues, including developmental delays and infertility. Other sex chromosome monosomies are rare.