Human Chromosome 21

**Semantic type:** Cell Component

**Definition:** The designation for each member of the second smallest human autosomal chromosome pair. Chromosome 21 spans around 47 million nucleotides and represents about 1.5% of the total DNA in normal diploid cells.

**Synonyms:** - Chromosome 21 - Chromosome 21 - Chromosome 21 - chr21 - chr21 - chr21