By Dr Ananya Mandal, MD
Chromosome 2 is one of the 23 pairs of chromosomes that make up the 46 chromosomes present in human cells. Chromosome 2 is the second largest of the human chromosomes, spanning 243 million base pairs and making up around 8% of the total DNA present within our cells. The base pairs are the DNA building blocks and are tightly packed, coiled and super coiled to form the structure of the DNA helix.
Genetic research is focused on identifying the genes on our chromosomes and estimates suggest that chromosome 2 contains around 1490 genes which include the HOXD homeobox gene cluster. Several important diseases and conditions have been linked to gene abnormalities on chromosome 2, including maturity onset diabetes of the young, primary pulmonary hypertension and autism.
Within the primate family hominidae, 24 pairs of chromosomes are seen in all species apart from humans and the extinct Neanderthals and Denisovan species, where 23 pairs of chromosomes make up the genome.
A widely accepted theory is that chromosome 2 was formed by the fusion of two ancestral chromosomes. Evidence supporting this includes the fact that the chimpanzee, gorilla and orangutan all have near-identical gene sequences to those found on human chromosome 2, but the sequences are located on two different chromosomes. In addition, human chromosome 2 has the remnants of a second centromere instead of the usual one centromere. Finally, chromosome 2 in humans has telomeres at its centre as well as at its ends, when usually telomeres are only found at the ends of a chromosome.
Reviewed by Sally Robertson, BSc