Monoszómiáról

Monoszómia refers to a form of aneuploidy where an individual has only one copy of a particular chromosome instead of the usual two. This is in contrast to disomy, which is the normal state of having two copies of each chromosome. Monosomy can occur for any of the autosomal chromosomes (non-sex chromosomes) or for the sex chromosomes.

The most common and well-known example of autosomal monosomy in humans is Monosomy 21. However, complete monosomy for most autosomal chromosomes is usually lethal and results in miscarriage. Monosomy X, also known as Turner syndrome, is a viable condition affecting females. Individuals with Turner syndrome have only one X chromosome, leading to a range of developmental differences.

Monosomy arises due to errors during meiosis, the process of cell division that produces gametes (sperm and egg cells). Specifically, it occurs when homologous chromosomes fail to separate properly during anaphase I of meiosis (nondisjunction), or when sister chromatids fail to separate during anaphase II. This results in a gamete with one fewer chromosome than normal. If this gamete is involved in fertilization, the resulting zygote will have only one copy of that chromosome.

The consequences of monosomy depend on which chromosome is affected. Autosomal monosomies are generally severe and incompatible with life, except in very rare cases of mosaicism where only some cells have the missing chromosome. Sex chromosome monosomies, like Monosomy X, can lead to specific syndromes with varying degrees of severity and phenotypic expression. Diagnosis is typically made through genetic testing such as karyotyping.