The Library

All 24 human
chromosomes.

Humans carry 22 autosomal chromosomes plus one pair of sex chromosomes - 46 chromosomes in every nucleated cell, from the largest (chromosome 1) down to the smallest sex chromosome (Y). Each page sets out size, gene content, notable cytogenetic bands, and the chromosomal disorders that arise when things go wrong.

249.0 Mb · ~2,058 genes

The largest human chromosome - ~8% of the genome and the most gene-dense by absolute count.

242.2 Mb · ~1,309 genes

Second-largest chromosome - a fusion of two ancestral primate chromosomes, unique to humans.

198.3 Mb · ~1,078 genes

Mid-size metacentric chromosome - home of the Lynch-syndrome mismatch-repair gene MLH1 and the VHL tumour suppressor.

190.2 Mb · ~752 genes

Site of the HTT gene - home of Huntington disease, the archetypal trinucleotide-repeat disorder.

181.5 Mb · ~876 genes

Home of the APC gene (familial adenomatous polyposis) and SMN1 (spinal muscular atrophy).

170.8 Mb · ~1,047 genes

Carries the HLA (MHC) region - the most polymorphic locus in the human genome and a central player in immunity.

159.3 Mb · ~989 genes

Home of CFTR (cystic fibrosis) and the Williams-syndrome critical region.

145.1 Mb · ~685 genes

Home of the MYC oncogene at 8q24 - one of the most-studied cancer drivers in biology.

138.4 Mb · ~785 genes

Home of the 9p21 cardiovascular/cancer locus and the ABL1 partner in the Philadelphia translocation.

133.8 Mb · ~735 genes

Home of the PTEN tumour-suppressor (Cowden syndrome) and RET (MEN 2).

135.1 Mb · ~1,320 genes

Unusually gene-dense - includes the β-globin cluster (sickle-cell disease, β-thalassaemia), WT1, and ATM.

133.3 Mb · ~1,034 genes

Home of the KRAS oncogene and the PKU-causing PAH locus.

114.4 Mb · ~327 genes

Acrocentric - carries BRCA2 and RB1, and is the chromosome involved in Patau syndrome (trisomy 13).

107.0 Mb · ~820 genes

Acrocentric - carries the α1-antitrypsin locus (SERPINA1) and the immunoglobulin heavy-chain cluster.

102.0 Mb · ~613 genes

The imprinting chromosome - parent-of-origin expression at 15q11-13 causes both Prader-Willi and Angelman syndromes.

90.3 Mb · ~866 genes

Home of the α-globin cluster, PKD1 (polycystic kidney disease), and the 16p11.2 autism-risk locus.

83.3 Mb · ~1,186 genes

The tumour-suppressor chromosome - BRCA1, TP53, and NF1 all sit here. Dense with clinical-genetics landmarks.

80.4 Mb · ~268 genes

Gene-sparse - but carries SMAD4 (juvenile polyposis) and is the chromosome of Edwards syndrome (trisomy 18).

58.6 Mb · ~1,474 genes

The most gene-dense chromosome in the human genome - carries APOE (Alzheimer/cardiovascular risk) and LDLR (familial hypercholesterolaemia).

64.4 Mb · ~544 genes

Compact metacentric - home of PRNP (prion diseases) and JAG1 (Alagille syndrome).

46.7 Mb · ~234 genes

The smallest human autosome - trisomy 21 causes Down syndrome, the most common survivable chromosomal disorder.

50.8 Mb · ~488 genes

The first human chromosome fully sequenced - home of the 22q11.2 DiGeorge-syndrome region and the BCR partner of BCR-ABL.

156.0 Mb · ~839 genes

Submetacentric · Sex-linked

The female-determining sex chromosome - one of two X’s in typical females, one of two sex chromosomes in typical males. Undergoes X-inactivation to equalise gene dosage.

57.2 Mb · ~63 genes

Acrocentric · Sex-linked

The male-determining sex chromosome - small, gene-poor, and largely heterochromatic. Carries SRY, the testis-determining gene.