Chromosome 2 is one of the twenty-three pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 2 is the second-largest human chromosome, spanning more than 242 million base pairs^[4] and representing almost eight percent of the total DNA in human cells.

Chromosome 2 contains the HOXD homeobox gene cluster.^[5]

Humans have only twenty-three pairs of chromosomes, while all other extant members of Hominidae have twenty-four pairs.^[6] It is believed that Neanderthals and Denisovans had twenty-three pairs.^[6]

Human chromosome 2 is a result of an end-to-end fusion of two ancestral chromosomes.^[7][8][9] The evidence for this includes:

• The correspondence of chromosome 2 to two ape chromosomes. The closest human relative, the chimpanzee, has nearly identical DNA sequences to human chromosome 2, but they are found in two separate chromosomes. The same is true of the more distant gorilla and orangutan.^[10][11]
• The presence of a vestigial centromere. Normally a chromosome has just one centromere, but in chromosome 2 there are remnants of a second centromere in the q21.3–q22.1 region.^[12]
• The presence of vestigial telomeres. These are normally found only at the ends of a chromosome, but in chromosome 2 there are additional telomere sequences in the q13 band, far from either end of the chromosome.^[13]

We conclude that the locus cloned in cosmids c8.1 and c29B is the relic of an ancient telomere-telomere fusion and marks the point at which two ancestral ape chromosomes fused to give rise to human chromosome 2.

— Jacob W. Ijdo^[13]

This section needs additional citations for verification. (September 2015)

The following diseases and traits are related to genes located on chromosome 2: