  In genetic drift of small population, it is well known that even when the
ratio of alleles is 0.5, specific genes are fixed in or disappear from the
population. It seems the reason why inbreeding is avoided. On the other hand,
this phenomenon suggests an interesting possibility. The mutant gene does not
increase the number of genes at once in a large population. A gene is partially
fixed by increasing the number within a small population because of inbreeding,
and the gene increases in a large group by Darwin's natural selection. It would
be more reasonable to think in this way. We studied this mathematically based
on the concept of genetic drift. This suggested that inbreeding could be useful
as a trigger for fixation of mutation.
