The smallest human chromosome is chromosome 21.
Chromosome 21 is the smallest autosome in humans. Let's break that down:
- Autosome: Any of the numbered chromosomes, as opposed to the sex chromosomes (X and Y). Humans have 22 pairs of autosomes and one pair of sex chromosomes.
- Smallest: Chromosome 21 is relatively short compared to other chromosomes.
It contains approximately 48 million base pairs. Base pairs are the building blocks of DNA. While 48 million sounds like a lot, it represents only about 1.5 to 2 percent of the total DNA found in human cells. Chromosome 21 is crucial, even with its smaller size, because it houses genes responsible for important functions. Having an extra copy of chromosome 21 leads to Down syndrome, illustrating its significant role.
