Dosage-sensitive genes in evolution and disease

Table 1 Human autosomes with common trisomies, in ascending order of number of ohnologs

Human chromosome number	Number of dosage-balanced ohnologs^a	Trisomy syndrome	Frequency (number of live births)^b
21	61	Down's	1/700
18	98	Edward's	1/5000
13	138	Patau	1/16,000

^aIdentified from gene trees in Ensembl v86 [109] as genes that duplicated at the base of the vertebrate tree with no subsequent SSD
^bFrequency data from [90] and ghr.nlm.nih.gov/trisomy-18; ghr.nlm.nih.gov/trisomy-13

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