Chromosom

A chromosom is a thread-like molecule of DNA and protein that carries genetic information. In eukaryotic cells, chromosomen are linear and reside in the cell nucleus, where they are organized into chromatin by histone and other proteins. In prokaryotes, the chromosom is usually a single circular DNA molecule located in the cytoplasm’s nucleoid region.

Each chromosom has a centromere, the constricted region where kinetochores attach during cell division; telomeres cap the ends and protect DNA from degradation and unwanted fusion. The DNA is wrapped around histones to form nucleosomes and is further compacted into higher-order fibers. During replication, a chromosom is duplicated to form sister chromatids that stay joined at the centromere until later stages of division.

Chromosomen carry genes and regulatory elements that determine inherited traits and biological functions. They are classified as autosomes or sex chromosomes in many species; humans have 23 pairs (46 chromosomes): 22 autosome pairs and 1 pair of sex chromosomes (XX or XY). The complete set is referred to as a karyotype when visualized.

During cell division, chromosomen are replicated in the S phase and then segregated by mitosis or meiosis to ensure daughter cells receive an appropriate genetic complement. Errors in segregation can lead to aneuploidy, linked to disorders such as Down syndrome (trisomy 21), Turner syndrome (monosomy X), or Klinefelter syndrome (XXY).

Scientific study of chromosomen encompasses cytogenetics, sequencing, and chromosomal mapping, contributing to understanding heredity, development, and disease across diverse species.