Hostname: page-component-cd9895bd7-lnqnp Total loading time: 0 Render date: 2024-12-27T17:03:25.587Z Has data issue: false hasContentIssue false
  • English
  • Français

Inbreeding depression and the maintenance of deleterious genes by mutation: model of a Drosophila chromosome

Published online by Cambridge University Press:  14 April 2009

John A. Sved  and
Alan N. Wilton
John A. Sved
Affiliation:
School of Biological Sciences A 12, Sydney University, NSW 2006, Australia
Alan N. Wilton
Affiliation:
School of Biological Sciences A 12, Sydney University, NSW 2006, Australia
Rights & Permissions [Opens in a new window]

Summary

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Inbreeding experiments in Drosophila, particularly those carried out using the ‘balancer equilibration’ technique, have revealed high levels of inbreeding depression. It has been estimated that non-lethal chromosomes have a fitness of 20% or less in homozygous condition compared to chromosome heterozygotes. Deleterious recessive genes are, in principle, capable of explaining such inbreeding depression. In this paper we have asked quantitatively whether the observed high levels are consistent with what is known about numbers of loci and mutation rates. We find that accepted mutation rates are easily high enough, provided that the deleterious genes are fully recessive. Partial dominance, even to the extent of 10% or less, reverses this conclusion. These calculations have been made assuming the multiplicative model. However the arguments are potentially sensitive to certain types of selective interactions, and a model which proposes quadratic gene interaction allows for higher levels of partial dominance. We also test the effect of taking into account a further constraint. Crow and Mukai have argued from estimates of the persistence of new deleterious mutations affecting viability that heterozygotes have a reduction in fitness of around 1–2% per locus, similar to the estimate for lethal genes. Application of this additional constraint would markedly reduce the range of permissible selection coefficients. However we argue that the selective disadvantages in heterozygotes of most mutations affecting fitness are unlikely to be as high as estimated for mutations affecting viability.

Type
Research Article
Information
Genetics Research , Volume 53 , Issue 2 , April 1989 , pp. 119 - 128
Copyright
Copyright © Cambridge University Press 1989

References

Crow, J. F. (1948). Alternative hypotheses of hybrid vigor. Genetics 33, 477–487.CrossRefGoogle ScholarPubMed
Crow, J. F. (1979). Minor viability mutants in Drosophila. Genetics 92, s165–s172.Google ScholarPubMed
Crow, J. F. & Kimura, M. (1970). An Introduction to Population Genetics Theory. New York: Harper and Row.Google Scholar
Crow, J. F. & Simmons, M. J. (1983). The mutation load in Drosophila. In The Genetics and Biology of Drosophila, vol. III (ed. Ashburner, M. and Thompson, J. N.). New York: Academic Press.Google Scholar
Fisher, R. A. (1949). The Theory of Inbreeding. Edinburgh: Oliver and Boyd.Google Scholar
Fristrom, J. W. & Clegg, M. T. (1988). Principles of Genetics, 2nd edn.New York: Chiron.Google Scholar
Haymer, D. S. & Hartl, D. L. (1982). The experimental assessment of fitness in Drosophila. I. Comparative measures of competitive reproductive success. Genetics 102, 455–466.CrossRefGoogle ScholarPubMed
Judd, B. H., Shen, M. W. & Kaufman, T. C. (1972). The anatomy and function of a segment of the X chromosome of Drosophila melanogaster. Genetics 71, 139–156.CrossRefGoogle ScholarPubMed
Kimura, M. (1983). The Neutral Theory of Molecular Evolution. Cambridge University Press.CrossRefGoogle Scholar
Lefevre, G. & Watkins, W. (1986). The question of the total gene number in Drosophila melanogaster. Genetics 113, 869–895.CrossRefGoogle ScholarPubMed
Lewontin, R. C. (1974). The Genetic Basis of Evolutionary Change. New York: Columbia University Press.Google Scholar
Mitchell, J. A. & Simmons, M. J. (1977). Fitness effects of EMS-induced mutations on the X chromosome of Drosophila melanogaster. II. Hemizygous fitness effects. Genetics 87, 775–783.CrossRefGoogle ScholarPubMed
Mukai, T. (1969). The genetic structure of natural populations of Drosophila melanogaster. VII. Synergistic interaction of spontaneous mutant polygenes controlling viability. Genetics 61, 749–761.CrossRefGoogle ScholarPubMed
Mukai, T., Chigusa, S. I., Mettler, L. E. & Crow, J. F. (1972). Mutation rate and dominance of genes affecting viability of polygenes in Drosophila melanogaster. Genetics 72, 335–355.CrossRefGoogle Scholar
Robertson, A. (1962). Selection for heterozygotes in small populations. Genetics 47, 1291–1300.CrossRefGoogle ScholarPubMed
Simmons, M. J. & Crow, J. F. (1977). Mutations affecting fitness in Drosophila populations. Annual Review of Genetics 12, 289–328.Google Scholar
Sved, J. A. (1976). The relationship between genotype and fitness for heterotic models. In Population Genetics and Ecology (ed. Karlin, S. and Nevo, E.). New York: Academic Press.Google Scholar
Sved, J. A. & Ayala, F. J. (1970). A population cage test for heterosis in Drosophila pseudoobscura. Genetics 66, 97–113.CrossRefGoogle ScholarPubMed
Wilton, A. N., Joseph, M. G. & Sved, J. A. (1989). Can chromosomal heterosis in Drosophila be explained by deleterious recessive genes? Negative results from a dichromosomal population test. Genetical Research 53, 129–140.CrossRefGoogle Scholar
Wilton, A. N., Sved, J. A., Hu, K. & Ayala, F. J. (1987). Fitness of half chromosome homozygotes of D. melanogaster relative to balancer heterozygotes in population cages. Genetics 116, s46.Google Scholar
Young, M. W. & Judd, B. H. (1978). Nonessential sequences, genes, and the polytene chromosome bands of Drosophila melanogaster. Genetics 88, 723–742.CrossRefGoogle ScholarPubMed