Chromosome

Diagram of a replicated and condensed metaphase eukaryotic chromosome. (1) Chromatid – one of the two identical parts of the chromosome after S phase. (2) Centromere – the point where the two chromatids touch. (3) Short (p) arm. (4) Long (q) arm.

A chromosome (m/; from Ancient Greek: χρωμόσωμα, chromosoma, chroma means colour, soma means body) is a DNA molecule with part or all of the genetic material (genome) of an organism. Most eukaryotic chromosomes include packaging proteins which, aided by chaperone proteins, bind to and condense the DNA molecule to prevent it from becoming an unmanageable tangle.[1][2]

Chromosomes are normally visible under a light microscope only when the cell is undergoing the metaphase of cell division (where all chromosomes are aligned in the center of the cell in their condensed form).[3] Before this happens, every chromosome is copied once (S phase), and the copy is joined to the original by a centromere, resulting either in an X-shaped structure (pictured to the right) if the centromere is located in the middle of the chromosome or a two-arm structure if the centromere is located near one of the ends. The original chromosome and the copy are now called sister chromatids. During metaphase the X-shape structure is called a metaphase chromosome. In this highly condensed form chromosomes are easiest to distinguish and study.[4] In animal cells, chromosomes reach their highest compaction level in anaphase during segregation.[5]

Chromosomal recombination during meiosis and subsequent sexual reproduction play a significant role in genetic diversity. If these structures are manipulated incorrectly, through processes known as chromosomal instability and translocation, the cell may undergo mitotic catastrophe and die. Mutations in the cell can allow it to inappropriately evade apoptosis and lead to the progression of cancer.

Some use the term chromosome in a wider sense, to refer to the individualized portions of chromatin in cells, either visible or not under light microscopy. Others use the concept in a narrower sense, to refer to the individualized portions of chromatin during cell division, visible under light microscopy due to high condensation.

Etymology

The word chromosome (m/[6][7]) comes from the Greek χρῶμα (chroma, "colour") and σῶμα (soma, "body"), describing their strong staining by particular dyes.[8] The term was coined by von Waldeyer-Hartz,[9] referring to the term chromatin, which was introduced by Walther Flemming.

Emilio Battaglia (1917-2011)[10][11] points out that over time many of the most familiar caryological terms have become inadequate or illogical or, in some cases, etymologically incorrect so that they should be replaced by more adequate alternatives suggested by the present scientific progress. The author has been particularly disappointed by the illogicality of the present chromosomal (chromatin-chromosome) terminology based on, or inferred by, two terms, Chromatin (Flemming 1880) and Chromosom (Waldeyer 1888), both inappropriately ascribed to a basically non coloured state.[12]

Other Languages
Afrikaans: Chromosoom
Alemannisch: Chromosom
العربية: كروموسوم
asturianu: Cromosoma
azərbaycanca: Xromosom
تۆرکجه: کوروموزوم
Bân-lâm-gú: Jiám-sek-thé
башҡортса: Хромосома
беларуская: Храмасома
български: Хромозома
bosanski: Hromosom
brezhoneg: Kromozom
català: Cromosoma
čeština: Chromozom
Cymraeg: Cromosom
dansk: Kromosom
Deutsch: Chromosom
eesti: Kromosoom
Ελληνικά: Χρωμόσωμα
español: Cromosoma
Esperanto: Kromosomo
euskara: Kromosoma
فارسی: کروموزوم
français: Chromosome
Frysk: Gromosoom
Gaeilge: Crómasóm
galego: Cromosoma
客家語/Hak-kâ-ngî: Ngiam-set-thí
한국어: 염색체
Հայերեն: Քրոմոսոմ
हिन्दी: गुणसूत्र
hrvatski: Kromosomi
Bahasa Indonesia: Kromosom
isiXhosa: I-chromosome
íslenska: Litningur
italiano: Cromosoma
עברית: כרומוזום
Basa Jawa: Kromosom
ქართული: ქრომოსომა
Kiswahili: Chembeuzi
Kreyòl ayisyen: Kwomozòm
kurdî: Kromozom
Кыргызча: Хромосомалар
Latina: Chromosoma
latviešu: Hromosoma
lietuvių: Chromosoma
lumbaart: Cromosoma
magyar: Kromoszóma
македонски: Хромозом
मराठी: गुणसूत्र
Bahasa Melayu: Kromosom
Mìng-dĕ̤ng-ngṳ̄: Niēng-sáik-tā̤
монгол: Хромосом
မြန်မာဘာသာ: ခရိုမိုဆုမ်း
Nederlands: Chromosoom
नेपाली: गुणसूत्र
日本語: 染色体
Nordfriisk: Kromosoom
norsk: Kromosom
norsk nynorsk: Kromosom
occitan: Cromosòma
олык марий: Хромосом
oʻzbekcha/ўзбекча: Xromosomalar
ਪੰਜਾਬੀ: ਗੁਣਸੂਤਰ
پنجابی: کروموسوم
polski: Chromosom
português: Cromossomo
română: Cromozom
русский: Хромосома
Scots: Chromosome
shqip: Kromozomi
Simple English: Chromosome
slovenčina: Chromozóm
slovenščina: Kromosom
کوردی: کرۆمۆسۆم
српски / srpski: Хромозом
srpskohrvatski / српскохрватски: Kromosom
Basa Sunda: Kromosom
suomi: Kromosomi
svenska: Kromosom
Tagalog: Chromosome
татарча/tatarça: Хромосома
తెలుగు: వారసవాహిక
тоҷикӣ: Хромосома
Türkçe: Kromozom
українська: Хромосома
Tiếng Việt: Nhiễm sắc thể
Winaray: Kromosoma
ייִדיש: כראמאזאם
Yorùbá: Krómósómù
粵語: 染色體
中文: 染色体