Chromosoms

Chromosoms, a term sometimes used interchangeably with chromosomes, are the carriers of genetic information in cells. In biology, they are made of DNA tightly associated with proteins and organized into a compact, threadlike form. In eukaryotes, most chromosomes reside in the cell nucleus, while organelles such as mitochondria can contain small, circular chromosomes. Prokaryotes typically have a single, circular chromosome located in the cytoplasm.

A chromosome at the level of structure consists of a DNA molecule and its associated proteins, forming chromatin. In preparation for cell division, chromosomes condense so that each one contains two sister chromatids joined at the centromere. These chromatids are separated during mitosis or meiosis to produce genetically separate daughter cells.

The genome is organized into a set of chromosomes, known as the karyotype. Humans have 23 pairs of chromosomes (46 total): 22 autosomes and 1 pair of sex chromosomes (XX in females, XY in males). Other species carry different numbers and arrangements of chromosomes. Genes are located along chromosomes and can be spaced far apart or clustered; noncoding regions also play roles in regulation and genome architecture.

Functions include storing and transmitting genetic information, guiding development and physiology, and regulating gene expression. Chromosomes are replicated once per cell cycle, ensuring identical copies are distributed to daughter cells. Structural changes, such as deletions, duplications, translocations, or whole-chromosome aneuploidies, can lead to developmental disorders or contribute to disease. Notable examples include Down syndrome (trisomy 21) and Turner syndrome (monosomy X).