Chromosome 2 is one of the twenty-three pairs of

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

s in

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

s. People normally have two copies of this chromosome. Chromosome 2 is the second-largest human chromosome, spanning more than 242 million

base pair A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...

s and representing almost eight percent of the total

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

in human cells. Chromosome 2 contains the HOXD

homeobox A homeobox is a Nucleic acid sequence, DNA sequence, around 180 base pairs long, that regulates large-scale anatomical features in the early stages of embryonic development. Mutations in a homeobox may change large-scale anatomical features of ...

gene cluster.Vega Homo sapiens genome browser: HoxD cluster on Chromosome 2
/ref>

Fusion

Humans have only twenty-three pairs of chromosomes, while all other extant members of

Hominidae The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic Family (biology), family of primates that includes eight Neontology#Extant taxa versus extinct taxa, extant species in four Genus, genera: ''Orangutan ...

have twenty-four pairs. It is believed that

Neanderthal Neanderthals ( ; ''Homo neanderthalensis'' or sometimes ''H. sapiens neanderthalensis'') are an extinction, extinct group of archaic humans who inhabited Europe and Western and Central Asia during the Middle Pleistocene, Middle to Late Plei ...

s and

Denisovan The Denisovans or Denisova hominins ( ) are an extinct species or subspecies of archaic human that ranged across Asia during the Lower and Middle Paleolithic, and lived, based on current evidence, from 285 thousand to 25 thousand years ago. D ...

s 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 Apes (collectively Hominoidea ) are a superfamily of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and Europe in prehistory, and counting humans are found global ...

chromosomes. The closest human relative, the

chimpanzee The chimpanzee (; ''Pan troglodytes''), also simply known as the chimp, is a species of Hominidae, great ape native to the forests and savannahs of tropical Africa. It has four confirmed subspecies and a fifth proposed one. When its close rel ...

, has nearly identical

DNA sequence A nucleic acid sequence is a succession of bases within the nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. This succession is denoted by a series of a set of five different letters that indicate the order of the nu ...

s to human chromosome 2, but they are found in two separate chromosomes. The same is true of the more distant

gorilla Gorillas are primarily herbivorous, terrestrial great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four or five su ...

and

orangutan Orangutans are great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in the genus ...

.Human and Ape Chromosomes
; accessed 8 September 2007. * The presence of a

vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...

centromere The centromere links a pair of sister chromatids together during cell division. This constricted region of chromosome connects the sister chromatids, creating a short arm (p) and a long arm (q) on the chromatids. During mitosis, spindle fiber ...

. 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

telomere A telomere (; ) is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes (see #Sequences, Sequences). Telomeres are a widespread genetic feature most commonly found in eukaryotes. In ...

s. 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.

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

prediction A prediction (Latin ''præ-'', "before," and ''dictum'', "something said") or forecast is a statement about a future event or about future data. Predictions are often, but not always, based upon experience or knowledge of forecasters. There ...

s of the

number of genes In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: prote ...

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.

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 Autism, also known as autism spectrum disorder (ASD), is a neurodevelopmental disorder characterized by differences or difficulties in social communication and interaction, a preference for predictability and routine, sensory processing d ...

Alport syndrome Alport syndrome is a genetic disorder affecting around 1 in 5,000–10,000 children, characterized by glomerulonephritis, end-stage kidney disease, and hearing loss. Alport syndrome can also affect the eyes, though the changes do not usually affec ...

* Alström syndrome *

Amyotrophic lateral sclerosis Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) or—in the United States—Lou Gehrig's disease (LGD), is a rare, Terminal illness, terminal neurodegenerative disease, neurodegenerative disorder that results i ...

* Brachydactyly type D *

Cleft chin The chin is the forward pointed part of the anterior mandible ( mental region) below the lower lip. A fully developed human skull has a chin of between 0.7 cm and 1.1 cm. Evolution The presence of a well-developed chin is considered to be one ...

Congenital hypothyroidism Congenital hypothyroidism (CH) is thyroid hormone deficiency present at birth. If untreated for several months after birth, severe congenital hypothyroidism can lead to growth failure and permanent intellectual disability. Infants born with co ...

Crigler–Najjar syndrome Crigler–Najjar syndrome is a rare inherited autosomal recessive disorder affecting the metabolism of bilirubin, a chemical formed from the breakdown of the heme in red blood cells. The disorder results in a form of non hemolytic jaundice, whic ...

types I/II *

Dementia with Lewy bodies Dementia with Lewy bodies (DLB) is a type of dementia characterized by changes in sleep, behavior change (individual), behavior, cognition, movement, and dysautonomia, regulation of automatic bodily functions. Unlike some other dementias, mem ...

Ehlers–Danlos syndrome Ehlers–Danlos syndromes (EDS) is a group of 14 genetic connective-tissue disorders. Symptoms often include loose joints, joint pain, stretchy velvety skin, and abnormal scar formation. These may be noticed at birth or in early childhood. Co ...

* Ehlers–Danlos syndrome, classical type * Ehlers–Danlos syndrome, vascular type * Fibrodysplasia ossificans progressiva *

Gilbert's syndrome Gilbert syndrome (GS) is a syndrome in which the liver of affected individuals processes bilirubin more slowly than the majority resulting in higher levels in the blood. Many people never have symptoms. Occasionally jaundice (a yellowing of the ...

Harlequin-type ichthyosis Harlequin-type ichthyosis is a genetic disorder that results in thickened skin over nearly the entire body at birth. The skin forms large, diamond/trapezoid/rectangle-shaped plates that are separated by deep cracks. These affect the shape of th ...

Hemochromatosis Iron overload is the abnormal and increased accumulation of total iron in the body, leading to organ damage. The primary mechanism of organ damage is oxidative stress, as elevated intracellular iron levels increase free radical formation via the ...

* Hemochromatosis type 4 *

Hereditary nonpolyposis colorectal cancer Hereditary nonpolyposis colorectal cancer (HNPCC) is a hereditary predisposition to colon cancer. HNPCC includes (and was once synonymous with) Lynch syndrome, an autosomal dominant genetic condition that is associated with a high risk of colon ...

* Infantile-onset ascending hereditary spastic paralysis * Juvenile primary lateral sclerosis *

Lactose intolerance Lactose intolerance is caused by a lessened ability or a complete inability to digest lactose, a sugar found in dairy products. Humans vary in the amount of lactose they can tolerate before symptoms develop. Symptoms may include abdominal pain ...

* 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 The photic sneeze reflex (also known as ACHOO syndrome, a contrived acronym for Autosomal-dominant Compelling Helio-Ophthalmic Outburst) is an inherited and congenital autosomal dominant reflex condition that causes sneezing in response to numer ...

Primary hyperoxaluria Primary hyperoxaluria is a rare condition (autosomal recessive) resulting in increased excretion of oxalate (up to 600 mg a day from normal 50 mg a day), with oxalate stones being common. Signs and symptoms Primary hyperoxaluria is an a ...

* Primary pulmonary hypertension * Sitosterolemia (knockout of either ABCG5 or ABCG8) *

Sensenbrenner syndrome Sensenbrenner syndrome (OMIM #218330) is a rare (less than 20 cases reported by 2010) multisystem disease first described by Judith A. Sensenbrenner in 1975. It is inherited in an autosomal recessive fashion, and a number of genes appear to be resp ...

Synesthesia Synesthesia (American English) or synaesthesia (British English) is a perceptual phenomenon in which stimulation of one sensory or cognitive pathway leads to involuntary experiences in a second sensory or cognitive pathway. People with sy ...

Waardenburg syndrome Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or Heterochromia iridum, one blue eye and one brown ey ...