Abstract
The heterozygous effects on fitness of second chromosomes carrying mutants induced with different doses of EMS were ascertained by monitoring changes in chromosome frequencies over time. These changes were observed in populations in which the treated chromosomes, as well as untreated competitors, remained heterozygous in males generation after generation. This situation was achieved by using a translocation which links the second chromosome to the X chromosome; however, only untranslocated second chromosomes were mutagenized. Chromosomes were classified according to their effects on viability in homozygous condition. A preliminary homozygosis identified completely lethal chromosomes; secondary tests distinguished between drastic (viability index < 0.1) and nondrastic chromosomes. Chromosomes that were nondrastic after treatment were found to reduce the fitness of their heterozygous carriers by 3–5%. The data show that flies homozygous for these chromosomes were about 2.7% less viable per treatment with 1 mm EMS than flies homozygous for untreated chromosomes. By comparing the fitness-depressing effects of nondrastic EMS-induced mutants in heterozygous condition with the corresponding viability-depressing effects measured by Temin, it is apparent that the total fitness effects are several times larger than the viability effects alone. Completely lethal chromosomes derived from the most heavily treated material reduced fitness by 11% in heterozygous condition; approximately half of this reduction was due to the lethal mutations themselves.
Full Text
The Full Text of this article is available as a PDF (1.1 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- 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]
- Maruyama T., Crow J. F. Heterozygous effects of x-ray induced mutations on viability of Drosophila melanogaster. Mutat Res. 1975 Feb;27(2):241–248. doi: 10.1016/0027-5107(75)90083-4. [DOI] [PubMed] [Google Scholar]
- Sved J. A. An estimate of heterosis in Drosophila melanogaster. Genet Res. 1971 Aug;18(1):97–105. doi: 10.1017/s0016672300012453. [DOI] [PubMed] [Google Scholar]
- Sved J. A. Fitness of third chromosome homozygotes in Drosophila melanogaster. Genet Res. 1975 Apr;25(2):197–200. doi: 10.1017/s0016672300015603. [DOI] [PubMed] [Google Scholar]