Kromosoom

Kromosoom is a thread-like structure that contains the genetic material of an organism. In eukaryotic cells, kromosoom is located in the cell nucleus and consists of DNA wrapped around proteins called histones, forming chromatin. The DNA carries genes, regulatory elements, and noncoding sequences. Kromosooms are organized into linear structures, and during cell division they condense further to form visible chromosomes. In prokaryotes, the chromosome is typically a single circular DNA molecule located in the nucleoid region, and many bacteria also harbor smaller circular DNA molecules called plasmids.

A kromosoom typically includes a centromere, telomeres at its ends, and regions of euchromatin and heterochromatin. The centromere is where kinetochores attach during division; telomeres protect chromosome ends from degradation. Chromatin state influences gene expression; euchromatin is generally transcriptionally active, while heterochromatin is more condensed and silent.

Chromosome number and composition vary by species. In humans, somatic cells carry 46 chromosomes (23 pairs): 22 autosome pairs and 1 pair of sex chromosomes (XX in most females, XY in most males). A karyotype is an organized profile of a organism’s chromosome set. During meiosis, recombination and segregation create haploid gametes.

Genetic disorders can arise from abnormalities in chromosome number or structure. Aneuploidy, such as trisomy 21 in Down syndrome, monosomy X in Turner syndrome, or extra sex chromosomes in Klinefelter syndrome, results from errors in segregation. Structural changes include deletions, duplications, inversions, and translocations, which can disrupt genes or regulatory regions.