Within-generation mutation variance for litter size in inbred mice

The mutational input of genetic variance per generation (²_m) is the lower limit of the genetic variability in inbred strains of mice, although greater values could be expected due to the accumulation of new mutations in successive generations. A mixed model analysis using Bayesian methods was applied to estimate ²_m and the across-generation accumulated genetic variability on litter size in 46 generations of a C57BL/6J inbred strain. This allowed for a separate inference on ²_m and on the additive genetic variance in the base population (²_a). The additive genetic variance in the base generation was 0.151 and quickly decreased to almost null estimates in generation 10. On the other hand, ²_m reached a moderate estimate (0.035) and the within-generation mutational variance increased up to generation 14, showing an oscillating draw between 0.102 and 0.234 during the remaining generations. This pattern agreed with ²_a in the base population and suggested the existence of a continuous uploading of genetic variability for litter size (h² = 0.045 ). Relevant genetic drift was not detected in this population. In conclusion, our approach allowed for a separate estimation of ²_a and ²_m within the mixed model framework, and the heritability obtained highlighted the significant and continuous influence of new genetic variability impacting the genetic stability of inbred strains.

Key Words: C57BL/6J, genetic stability, genetic variability, inbred strain, mutation

Online ISS 1091-6490
Copyright 2008 by the Genetics Society of America
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