Chromosome 20
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Chromosome 20 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 20 spans around 63 million base pairs (the building material of DNA) and represents between 2 and 2.5 percent of the total DNA in cells.

Identifying genes on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. Chromosome 20 contains over 900 genes. New discoveries have recently linked this chromosome to the increasing susceptability to male-pattern baldness.

Genes

The following are some of the genes located on chromosome 20:

• EDN3: endothelin 3
• JAG1: jagged 1 (Alagille syndrome)
• PANK2: pantothenate kinase 2 (Hallervorden-Spatz syndrome)
• PRNP: prion protein (p27-30) (Creutzfeld-Jakob disease, Gerstmann-Strausler-Scheinker syndrome, fatal familial insomnia)
• tTG:tissue transglutaminase (Celiac disease)
• AHCY: S-adenosylhomocysteine hydrolase
• ARFGEF2: ADP-ribosylation factor guanine nucleotide-exchange factor 2 (brefeldin A-inhibited)
• GSS: glutathione synthetase
• SALL4: sal-like 4 (Drosophila)
• VAPB: VAMP (vesicle-associated membrane protein)-associated protein B and C
• BMP2: Bone Morphogenetic Protein 2 (osteoblast differentiation)
• GNAS1: Gs alpha subunit (membrane G-protein)

Diseases & disorders

The following diseases are some of those related to genes on chromosome 20:

• Adenosine deaminase deficiency
• Alagille syndrome
• Celiac disease
• Maturity onset diabetes of the young type 1
• Pantothenate kinase-associated neurodegeneration
• Transmissible spongiform encephalopathy (prion diseases)
• Waardenburg syndrome

References

• Deloukas, P. et al (2001). "The DNA sequence and comparative analysis of human chromosome 20". Nature 414 (6866): 865–71. doi:10.1038/414865a. PMID 11780052. 
• Gilbert, F. (1997). "Disease genes and chromosomes: disease maps of the human genome". Genet Test 1 (3): 225–9. PMID 10464650. 

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