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Chicken W: a genetically uniform chromosome in a highly variable genome.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Biology.
(English)Manuscript (Other (popular science, discussion, etc.))
URN: urn:nbn:se:uu:diva-92043OAI: oai:DiVA.org:uu-92043DiVA: diva2:164987
Available from: 2004-09-07 Created: 2004-09-07 Last updated: 2010-01-14Bibliographically approved
In thesis
1. The Effects of Mutation and Selection on the Rate and Pattern of Molecular Evolution in Birds
Open this publication in new window or tab >>The Effects of Mutation and Selection on the Rate and Pattern of Molecular Evolution in Birds
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

By comparing sequence diversity and divergence on sex chromosomes one can study how the rate of evolution in affected by mutation and/or selection. The rate of mutation in male biased, meaning that relatively more mutations are created in the male germ line than in the female. Since the male mutation bias (αm) most likely is a consequence of the difference in cell divisions between male and female germ lines, life history characters that affect this difference should covary with αm. Indeed, we found a positive correlation between estimates of αm and increased generation times and increased intensity of sperm competition. We have also found that estimates of αm varied significantly between gametologous introns located on the sex chromosomes. This could be a consequence of the variation in substitution rates between loci.

Population genetics theory predicts that both positive and negative selection reduce genetic diversity around a selected locus at a distance determined by the rate of recombination. Consequently, a non-recombining chromosome, like the female specific W chromosome in birds, selection is expected to have a large impact on sequence diversity. Indeed, in a large sequence screening we found only one segregating site among 7643 base pairs sequenced in 47 chicken females. Furthermore, we also found that deleterious substitutions are fixed in a higher rate for W- than Z-linked sequences, which is in agreement with the lack of recombination and strong genetic drift due to the low effective population size.

Rarely non-synonymous mutations are beneficial for an individual, but when it happens, the mutation is positively selected and rapidly reaches fixation in a population. We have found that positive selection has been acting on the female reproductive protein, zona pellucida c in birds. This rapid evolution is likely a mechanism to prevent hybridisation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 59 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1006
Molecular genetics, substitution rate, diversity, selection, male mutation bias, birds, Genetik
National Category
urn:nbn:se:uu:diva-4516 (URN)91-554-6021-6 (ISBN)
Public defence
2004-09-30, Friessalen, EBC, Norbyvagen 14, Uppsala, 10:15 (English)
Available from: 2004-09-07 Created: 2004-09-07 Last updated: 2009-03-31Bibliographically approved

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