--- _id: '3623' abstract: - lang: eng text: 'We present the theoretical background to a new method for measuring genetic variation for total fitness in Drosophila. The method allows heterozygous effects on total fitness of whole wild-type chromosomes to be measured under normal demography with overlapping generations. The wild-type chromosomes are competed against two balancer chromosomes (B1, B2, say), providing a standard genotype B1/B2 against which variation in the fitness effects of the wild-type chromosomes can be assessed. Fitness can be assessed in two ways: (i) at equilibrium of all three chromosomes under heterozygote advantage, and (ii) during displacement of one balancer by the other. Equilibrium with all three chromosomes present will be achieved only if the wild-type homozygote is not too fit, and if the fitnesses of the three heterozygotes are not too unequal. These conditions were not satisfied for any of a sample of 12 lethal-bearing chromosomes isolated from a random-bred laboratory population of Drosophila. At equilibrium, genotypic frequencies show low sensitivity to changes in genotypic fitness. Furthermore, where all four genotypes are viable and fertile, supplementary information from cages with only two chromosomes present and from direct measurements of pre-adult viability are required to estimate fitnesses from frequencies. The invasion method has the advantages of a greater sensitivity and of not requiring further data to estimate fitnesses if the wild-type homozygote is fertile. However, it requires that multiple samples be taken as the invasion progresses. In a discrete generation model, generation time influences fitness estimates from this method and is difficult to estimate accurately from the data. A full age-structured model can also be applied to the data from both types of experiment. For the invasion method, this gives fitness estimates close to those from the discrete generation model.' acknowledgement: This work was supported by grant GR31/G09821 from the BBSRC, and by fellowships from the Darwin Trust of Edinburgh and the NERC. We are grateful to the referees for their helpful comments on the manuscript. article_processing_charge: No article_type: original author: - first_name: Nicholas H full_name: Barton, Nicholas H id: 4880FE40-F248-11E8-B48F-1D18A9856A87 last_name: Barton orcid: 0000-0002-8548-5240 - first_name: Linda full_name: Patridge, Linda last_name: Patridge citation: ama: Barton NH, Patridge L. Measuring fitness by means of balancer chromosomes. Genetical Research. 2000;75(3):297-314. doi:10.1017/S0016672399004346 apa: Barton, N. H., & Patridge, L. (2000). Measuring fitness by means of balancer chromosomes. Genetical Research. Cambridge University Press. https://doi.org/10.1017/S0016672399004346 chicago: Barton, Nicholas H, and Linda Patridge. “Measuring Fitness by Means of Balancer Chromosomes.” Genetical Research. Cambridge University Press, 2000. https://doi.org/10.1017/S0016672399004346. ieee: N. H. Barton and L. Patridge, “Measuring fitness by means of balancer chromosomes,” Genetical Research, vol. 75, no. 3. Cambridge University Press, pp. 297–314, 2000. ista: Barton NH, Patridge L. 2000. Measuring fitness by means of balancer chromosomes. Genetical Research. 75(3), 297–314. mla: Barton, Nicholas H., and Linda Patridge. “Measuring Fitness by Means of Balancer Chromosomes.” Genetical Research, vol. 75, no. 3, Cambridge University Press, 2000, pp. 297–314, doi:10.1017/S0016672399004346. short: N.H. Barton, L. Patridge, Genetical Research 75 (2000) 297–314. date_created: 2018-12-11T12:04:18Z date_published: 2000-06-01T00:00:00Z date_updated: 2023-05-02T12:09:23Z day: '01' doi: 10.1017/S0016672399004346 extern: '1' external_id: pmid: - '10893866' intvolume: ' 75' issue: '3' language: - iso: eng month: '06' oa_version: None page: 297 - 314 pmid: 1 publication: Genetical Research publication_identifier: issn: - 0016-6723 publication_status: published publisher: Cambridge University Press publist_id: '2760' quality_controlled: '1' scopus_import: '1' status: public title: Measuring fitness by means of balancer chromosomes type: journal_article user_id: ea97e931-d5af-11eb-85d4-e6957dddbf17 volume: 75 year: '2000' ...