21号染色体

人类的21号染色体是23对染色体的其中之一，正常状况下每个细胞拥有两条。此染色体是所有人类染色体中最小的一个，含有大约4700万个碱基对，占细胞内所有DNA的1.5%。

21号染色体
物种	Homo sapiens
基因数量	200-400

21号染色体的定序是在2000年宣布完成，是人类基因组计划中第二条定序完成的人类染色体。此染色体内大约含有300到400个基因，依预测方式而有所不同。

相关疾病

• 阿兹海默症第一型
• 肌肉萎缩性侧索硬化症（渐冻人症）第一型
• 唐氏症候群
• Holocarboxylase synthetase deficiency
• Homocystinuria
• Jervell and Lange-Nielsen syndrome
• Leukocyte adhesion deficiency
• Nonsyndromic deafness
• Nonsyndromic deafness, autosomal recessive
• Romano-Ward syndrome

参考文献

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