Kromoszómaszám

Kromoszómaszám refers to the specific number of chromosomes found within the nucleus of a cell of a particular species. In most eukaryotic organisms, chromosomes are arranged in homologous pairs. The somatic cells, which are all body cells except for gametes, typically contain a diploid number of chromosomes, denoted as 2n. This means that for each type of chromosome, there are two copies, one inherited from each parent. Gametes, on the other hand, which are reproductive cells like sperm and egg, are haploid and contain only a single set of chromosomes, denoted as n. This reduction in chromosome number during gamete formation is crucial for sexual reproduction, ensuring that when a sperm and egg fuse during fertilization, the resulting zygote restores the diploid number characteristic of the species.

Variations in chromosome number can occur. Aneuploidy is a condition where an individual has an abnormal number of chromosomes, meaning they have either more or fewer chromosomes than is typical for their species. This can involve the gain or loss of one or more entire chromosomes. For example, Down syndrome in humans is caused by trisomy 21, where individuals have three copies of chromosome 21 instead of the usual two. Polyploidy, another type of variation, involves having more than two complete sets of chromosomes. This is more common in plants and can lead to larger size and other altered traits. The precise kromoszómaszám is a fundamental characteristic of a species, playing a vital role in genetic inheritance and cellular function.