Abstract
Spontaneous mutations were allowed to accumulate in a second chromosome that was transmitted only through heterozygous males for 40 generations. At 10-generation intervals the chromosomes were assayed for homozygous effects of the accumulated mutants. From the regression of homozygous viability on the number of generations of mutant accumulation and from the increase in genetic variance between replicate chromosomes it is possible to estimate the mutation rate and average effect of the individual mutants. Lethal mutations arose at a rate of 0.0060 per chromosome per generation. The mutants having small effects on viability are estimated to arise with a frequency at least 10 times as high as lethals, more likely 20 times as high, and possibly many more times as high if there is a large class of very nearly neutral mutations.—The dominance of such mutants was measured for chromosomes extracted from a natural population. This was determined from the regression of heterozygous viability on that of the sum of the two constituent homozygotes. The average dominance for minor viability genes in an equilibrium population was estimated to be 0.21. This is lower than the value for new mutants, as expected since those with the greatest heterozygous effect are most quickly eliminated from the population. That these mutants have a disproportionately large heterozygous effect on total fitness (as well as on the viability component thereof) is shown by the low ratio of the genetic load in equilibrium homozygotes to that of new mutant homozygotes.
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Selected References
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- Hiraizumi Y, Crow J F. Heterozygous Effects on Viability, Fertility, Rate of Development, and Longevity of Drosophila Chromosomes That Are Lethal When Homozygous. Genetics. 1960 Aug;45(8):1071–1083. doi: 10.1093/genetics/45.8.1071. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MUKAI T. THE GENETIC STRUCTURE OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER. I. SPONTANEOUS MUTATION RATE OF POLYGENES CONTROLLING VIABILITY. Genetics. 1964 Jul;50:1–19. doi: 10.1093/genetics/50.1.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Morton N. E., Chung C. S., Friedman L. D., Morton N. T., Miki C., Yee S. Relation between homozygous viability and average dominance in Drosophila melanogaster. Genetics. 1968 Nov;60(3):601–614. doi: 10.1093/genetics/60.3.601. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Morton N. E., Crow J. F., Muller H. J. AN ESTIMATE OF THE MUTATIONAL DAMAGE IN MAN FROM DATA ON CONSANGUINEOUS MARRIAGES. Proc Natl Acad Sci U S A. 1956 Nov;42(11):855–863. doi: 10.1073/pnas.42.11.855. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mukai T., Yamazaki T. The genetic structure of natural populations of Drosophila melanogaster. V. Coupling-repulsion effect of spontaneous mutant polygenes controlling viability. Genetics. 1968 Aug;59(4):513–535. doi: 10.1093/genetics/59.4.513. [DOI] [PMC free article] [PubMed] [Google Scholar]
- PAXMAN G. J. A study of spontaneous mutation in Drosophila melanogaster. Genetica. 1958;29(1-2):39–57. [PubMed] [Google Scholar]
- Temin R. G. Homozygous viability and fertility loads in Drosophila melanogaster. Genetics. 1966 Jan;53(1):27–46. doi: 10.1093/genetics/53.1.27. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Temin R. G., Meyer H. U., Dawson P. S., Crow J. F. The influence of epistasis on homozygous viability depression in Drosophila melanogaster. Genetics. 1969 Feb;61(2):497–519. doi: 10.1093/genetics/61.2.497. [DOI] [PMC free article] [PubMed] [Google Scholar]