|Budget Amount *help
¥28,100,000 (Direct Cost : ¥28,100,000)
Fiscal Year 1999 : ¥5,000,000 (Direct Cost : ¥5,000,000)
Fiscal Year 1998 : ¥6,900,000 (Direct Cost : ¥6,900,000)
Fiscal Year 1997 : ¥7,400,000 (Direct Cost : ¥7,400,000)
Fiscal Year 1996 : ¥8,800,000 (Direct Cost : ¥8,800,000)
(1) In, collaboration with Dr. Jan Klein in Max-Plank-Institut fur Biologie (Tubingen), the principal investigator (N. T.) has been co-authoring a popular science book for these four years. The book is entitled "Where do we come from? The molecular evidence for human descent" and is composed of 10 chapters. This year, the PI visited the MPI for three weeks to discuss the whole contents and write Chapter 6-10. The book covers several fields of biology, such as molecular biology, population genetics, anthropology, evolutionary genetics, and primatology. Many results obtained through this research project will be reproduced in the book. By the end of this calendar year, the book is planned to be distributed worldwide.
(2) In general, neutral genes in the human population exhibit relatively shallow genealogies. The time scale of such genealogies is of the order of N generations, where N is the effective population size and estimated as 10,000 during the Pleistocene. A notable exception is t
hose genes, which are linked to the Major Histocompatibility Complex (Mhc) loci. The genealogy at these linked neutral loci is much deeper than that of unlinked neutral genes. This, deep genealogy and high extent of nucleotide diversity result from linkage effects of balancing selection at Mhc loci. The nucleotide diversity of linked genes decreases, as the recombination rate between an Mhc locus and a linked neutral locus increases. Conversely, under an appropriate population genetics model, it is possible to estimate the recombination rate from the observed extent of the nucleotide diversity at a linked neutral locus. We have applied this principle to the human Mhc (HLA) region. The result shows that the recombination rate is generally 1 cM per 1 Mb, but it fluctuates considerably from locus to locus. In particular, the genomic region telomeric to the HLA-A locus is subjected to extremely infrequent recombination.
(3) We have expanded our previous analysis about the demographic history of human lineages during the entire period of primate evolution. We have constructed aDNA sequence database comprising of 45 sets of orthologous nucleotide sequences among the human, the chimpanzee, and the gorilla. It is confirmed that the chimpanzee is the closest relative to the human. However, individual sets of genes can support this conclusion only weakly. This weak support mainly stems from the presence of phylogenetically incompatible sites in an individual set of DNA sequences. The major cause of such sequence incompatibility is not due to homoplasy, but due to intragenic recombination among ancestral sequences. The trichotomy problem among the human, the chimpanzee, and the gorilla, or more generally among relatively closely related species can properly be addressed only within this framework. Less