形成細(xì)胞內(nèi)基因組或整個(gè)遺傳物質(zhì)的單體。染色體是通過(guò)纏繞蛋白質(zhì)而被包裝、壓縮而成的遺傳物質(zhì)或DNA長(zhǎng)鏈。染色體的數(shù)量和長(zhǎng)度隨物種而不同。人類(lèi)有23對(duì)染色體（每對(duì)染色體中的兩個(gè)單體分別來(lái)自父母雙方）。一對(duì)稱(chēng)為性染色體因?yàn)樗�包含決定性別的基因。攜帶決定男性的基因的染色體稱(chēng)為Y染色體，攜帶決定女性的基因的染色體稱(chēng)為X染色體。其余的染色體稱(chēng)為常染色體。1號(hào)染色體最大，22號(hào)染色體最小。每條染色體有兩臂稱(chēng)為p和q。

One of the physically separate segments that together form the genome, or total genetic material, of a cell. Chromosomes are long strands of genetic material or DNA that have been packaged and compressed by wrapping around proteins. The number and size of chromosomes varies from species to species. In humans, there are 23 pairs of chromosomes (a pair has one chromosome from each parent). One pair are called the sex chromosomes because they contain genes that determine sex. The chromosome carrying the male determining genes is designated Y and the corresponding female one the X chromosome. The remaining pairs are called autosomes. Chromosome 1 is the largest and chromosome 22 the smallest. Each chromosome has two “arms” designated p and q.