Ancient Origin of the Null Allele se
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of the Human ABO-Secretor Locus (FUT2) |
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Authors: | Yoshiro Koda Hidenori Tachida Mikiko Soejima Osamu Takenaka Hiroshi Kimura |
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Institution: | (1) Division of Human Genetics, Department of Forensic Medicine, Kurume University School of Medicine, Kurume 830-0011, Japan, JP;(2) Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan, JP;(3) Department of Biochemistry, Primate Research Institute, Kyoto University, Inuyama 484-0002, Japan, JP |
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Abstract: | In human populations, a null allele having several nucleotide differences from the wild-type allele is segregating at the
FUT2 locus (the ABO-Secretor locus) encoding α(1,2)fucosyltransferase. To estimate the age of the most recent common ancestor
(MRCA) of these two alleles, we sequenced FUT2 homologues from chimpanzee, gorilla, orangutan, and green monkey. Since we did not detect acceleration or any heterogeneity
in the substitution rate at this locus among these species, the age of the MRCA was estimated to be around 3 MYA, assuming
the divergence time of human and chimpanzee to be 5 MYA. We developed a simple test to examine whether or not the old age
of the MRCA of the FUT2 is consistent with that expected for two divergent neutral alleles sampled from a random mating population. An application
of the test to the data at FUT2 indicated that the age of the MRCA is too old to be explained by the simple neutral assumptions, although our test depends
on accurate estimation of the divergence time of human and chimpanzee in units of twice the human population size. Various
possibilities including balancing selection are discussed to explain this old age of the MRCA.
Received: 9 May 1999 / Accepted: 20 September 1999 |
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Keywords: | :FUT2 gene — Secretor gene — α (1 2)Fucosyltransferase — Old polymorphism — Balancing selection — Neutrality test |
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