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Updated: Jun 29, 2026

Assessing Differences in Sperm Competitive Ability in Drosophila
Published on: August 22, 2013
Human live birth and sperm-sex ratios compared
J Graffelman1, E F Fugger, K Keyvanfar
1University Pompeu Fabra, Department of Economics, Barcelona, Spain and Genetics & IVF Institute, 3020 Javier Road, Fairfax, VA 22031, USA.
Abstract:
The human secondary sex ratio is compared with the percentage of Y-chromosome bearing spermatozoa in human semen. Live birth sex ratio is about 51.3%, whereas the overall percentage of Y-chromosome bearing spermatozoa in our study samples was 50.3%, i.e. 1% closer to the proportion expected by Mendelian segregation. The observed difference between live birth and sperm-sex ratios was significant (P < 0.0001). A possible effect of male age on the percentage Y-bearing spermatozoa was found to be non-significant.
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