A theoretical method for evaluating the relative importance of positive selection and neutral drift from observed base changes |
| |
Authors: | Jinya Otsuka Satoshi Fukuchi Norihiro Kikuchi |
| |
Institution: | (1) Department of Applied Biological Science, Faculty of Science and Technology, Science University of Tokyo, Noda (278), Japan, JP |
| |
Abstract: | To evaluate the relative importance of positive selection and neutral drift from the nucleotide base changes observed in
the homologous alignment of genes, a theoretical equation of base changes is formulated by including both the influence of
selection and the base substitutions due to mutations. Under the assumption that the average rate of base substitutions estimated
from synonymous changes is the ``true' mutation rate applicable at all positions, this method is applied to the vertebrate
globin gene family, and evaluates the departures of base change rates from the ``true' mutation rate at the first and second
codon positions as a consequence of preferential selection for the conservation of important function. In addition to the
strong effect of selection on the amino acid residues in the internal region mostly common to myoglobin and hemoglobin chains,
the distinctive directions of selective parameter values are seen at sites on the globin surface, distinguishing the subunit
contact residues of hemoglobins from the polar residues on the surface of myoglobins. Moreover, this effect of selection distinguishing
between the myoglobin and hemoglobin chain genes becomes weaker in cold-blooded vertebrates, especially in fish, strongly
suggesting the possibility that the clear distinction between these globins is a result of selection out of the changes regarded
as neutral ones in an ancestor of vertebrates. Thus, the present method may also serve to investigate the homology of many
other proteins from the aspect of molecular evolution, mainly focusing on the evolution of their biological functions.
Received: 2 January 1996 / Accepted: 20 February 1997 |
| |
Keywords: | : Selection — Neutral drift — Globin genes — Convergence — Divergence |
本文献已被 SpringerLink 等数据库收录! |
|