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 and representing almost eight percent of the total DNA in human cells.

Chromosome 2 contains the HOXD homeobox gene cluster.Vega Homo sapiens genome browser: HoxD cluster on Chromosome 2

Fusion

Humans have only twenty-three pairs of chromosomes, while all other extant members of Hominidae have twenty-four pairs. Sequencing supports the idea that Neanderthals and Denisovans also had twenty-three pairs.

Human chromosome 2 is a result of an end-to-end fusion of two ancestral chromosomes.It has been hypothesized that Human Chromosome 2 is a fusion of two ancestral chromosomes by Alec MacAndrew; accessed 18 May 2006. 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.Human and Ape Chromosomes ; accessed 8 September 2007. 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. 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.

The timing of the fusion has been differently estimated by different researchers.

The telomere-to-telomere genome assembly and improved genome assembly techniques have enabled a closer look at the repeat-rich fusion site and the two ancestral centromere sites. The chimp and bonobo chromosome 2A and 2B respectively had an end region similar to chromosome 9 (p end) and chromosome 22 (q end). This likely happened in their common ancestor and was fueled by a pericentromeric inversion in each of their ends (the 2A inversion was only seen in these two species; the 2B inversion also in gorillas). The tips of these two end regions were themselves copies of a common ancestor and they were accidentally misaligned together in a human ancestor and lost. The residual segments similar to 9p24.3 and 22q13.33 around the fusion site support this idea. What appears as the modern vestigial telomere was already vestigial at the time of the fusion, as it was actually from the two ancient inversion events.

In 2026, it was reported that incomplete lineage sorting of segmental duplications defines the human chromosome 2 fusion site early during African great ape speciation.

Genes

Number of genes The following are some of the gene count estimates of human chromosome 2. Because researchers use different approaches to genome annotation, their predictions of the number of genes on each chromosome vary. Among various projects, the collaborative consensus coding sequence project (CCDS) takes an extremely conservative strategy. So CCDS's gene number prediction represents a lower bound on the total number of human protein-coding genes.

Estimated by Protein-coding genes Non-coding RNA genes Pseudogenes Source Release date CCDS 1,194 — — 2016-09-08 HGNC 1,196 450 931 2017-05-12 Ensembl 1,292 1,598 1,029 2017-03-29 UniProt 1,274 — — 2018-02-28 NCBI 1,281 1,446 1,207 2017-05-19

List of genes

The following is a partial list of genes on human chromosome 2. For complete list, see the link in the infobox on the right.

p-arm Partial list of the genes located on p-arm (short arm) of human chromosome 2:

q-arm Partial list of the genes located on q-arm (long arm) of human chromosome 2:

Related disorders and traits

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

2p15-16.1 microdeletion syndrome Autism Alport syndrome Alström syndrome Amyotrophic lateral sclerosis Brachydactyly type D Cleft chin Congenital hypothyroidism Crigler–Najjar syndrome types I/II Dementia with Lewy bodies Ehlers–Danlos syndrome Ehlers–Danlos syndrome, classical type Ehlers–Danlos syndrome, vascular type Fibrodysplasia ossificans progressiva Gilbert's syndrome Harlequin-type ichthyosis Hemochromatosis Hemochromatosis type 4 Hereditary nonpolyposis colorectal cancer Infantile-onset ascending hereditary spastic paralysis Juvenile primary lateral sclerosis Lactose intolerance Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency Lowry-Wood syndrome Maturity-onset diabetes of the young type 6 Mitochondrial trifunctional protein deficiency Nonsyndromic deafness Photic sneeze reflex Primary hyperoxaluria Primary pulmonary hypertension Sitosterolemia (knockout of either ABCG5 or ABCG8) Sensenbrenner syndrome Synesthesia Waardenburg syndrome Hypomyelination with brainstem and spinal cord involvement and leg spasticity

Cytogenetic band

+ G-bands of human chromosome 2 in resolution 850 bphs Chr. Arm"p": Short arm; "q": Long arm. BandFor cytogenetic banding nomenclature, see article locus. ISCNstartThese values (ISCN start/stop) are based on the length of bands/ideograms from . Arbitrary unit. ISCNstop Basepairstart Basepairstop Staingpos: Region which is positively stained by G banding, generally AT-rich and gene poor; gneg: Region which is negatively stained by G banding, generally CG-rich and gene rich; acen Centromere. var: Variable region; stalk: Stalk. Density 2 p 25.3 0 388 gneg 2 p 25.2 388 566 gpos 50 2 p 25.1 566 954 gneg 2 p 24.3 954 1193 gpos 75 2 p 24.2 1193 1312 gneg 2 p 24.1 1312 1565 gpos 75 2 p 23.3 1565 1789 gneg 2 p 23.2 1789 1908 gpos 25 2 p 23.1 1908 2027 gneg 2 p 22.3 2027 2296 gpos 75 2 p 22.2 2296 2415 gneg 2 p 22.1 2415 2609 gpos 50 2 p 21 2609 2966 gneg 2 p 16.3 2966 3220 gpos 100 2 p 16.2 3220 3294 gneg 2 p 16.1 3294 3548 gpos 100 2 p 15 3548 3757 gneg 2 p 14 3757 3935 gpos 50 2 p 13.3 3935 4114 gneg 2 p 13.2 4114 4248 gpos 50 2 p 13.1 4248 4353 gneg 2 p 12 4353 4860 gpos 100 2 p 11.2 4860 5307 gneg 2 p 11.1 5307 5545 acen 2 q 11.1 5545 5724 acen 2 q 11.2 5724 6022 gneg 2 q 12.1 6022 6261 gpos 50 2 q 12.2 6261 6395 gneg 2 q 12.3 6395 6559 gpos 25 2 q 13 6559 6812 gneg 2 q 14.1 6812 7036 gpos 50 2 q 14.2 7036 7334 gneg 2 q 14.3 7334 7602 gpos 50 2 q 21.1 7602 7826 gneg 2 q 21.2 7826 8050 gpos 25 2 q 21.3 8050 8169 gneg 2 q 22.1 8169 8437 gpos 100 2 q 22.2 8437 8497 gneg 2 q 22.3 8497 8646 gpos 100 2 q 23.1 8646 8735 gneg 2 q 23.2 8735 8795 gpos 25 2 q 23.3 8795 9078 gneg 2 q 24.1 9078 9361 gpos 75 2 q 24.2 9361 9585 gneg 2 q 24.3 9585 9928 gpos 75 2 q 31.1 9928 10435 gneg 2 q 31.2 10435 10599 gpos 50 2 q 31.3 10599 10733 gneg 2 q 32.1 10733 11091 gpos 75 2 q 32.2 11091 11225 gneg 2 q 32.3 11225 11538 gpos 75 2 q 33.1 11538 11925 gneg 2 q 33.2 11925 12060 gpos 50 2 q 33.3 12060 12283 gneg 2 q 34 12283 12641 gpos 100 2 q 35 12641 13014 gneg 2 q 36.1 13014 13237 gpos 75 2 q 36.2 13237 13297 gneg 2 q 36.3 13297 13595 gpos 100 2 q 37.1 13595 13893 gneg 2 q 37.2 13893 13998 gpos 50 2 q 37.3 13998 14400 gneg

References

External links