Abstract

Meiotic Recombination in Ruminant Livestock Species A.M. Rodriguez1, K.M. Davenport1, J.B. Glaze, Jr.1, S.D. McKay2, C.A. Gill3 & B.M. Murdoch*1 1University of Idaho, Department of Animal and Veterinary Science, ID, United States *bmurdoch@uidaho.edu (Corresponding Author) 2Univeristy of Vermont, Department of Animal and Veterinary Science, VT, United States 3Texas A&M University, Department of Animal Science, College Station, TX, United States Homologous recombination is an important component of gametogenesis that contributes to genetic variation, and ensures proper chromosome segregation. Despite the importance of this process, we know very little about the factors that control and/or influence global meiotic recombination/crossover (CO) in livestock. Previous research recognizes that a least one CO per chromosome arm is required to ensure proper chromosome segregation. Even though cattle and sheep are different species and beefalo are a cattle hybrid, they have the same number of chromosome arms. This study uses a direct cytological approach to quantify, and characterize the number of COs in beefalo, cattle, and sheep spermatocytes. Here we report that beefalo exhibit on average 5% fewer COs per spermatocyte compared to cattle, and cattle exhibit 28% fewer COs compared to sheep. Further, we examined the number of COs for each homologous chromosome pair in a subset of spermatocytes for each species. We found a positive correlation between the numbers of COs and the length of a chromosome. Overall, sheep exhibited as many as 9 COs per chromosome; whereas the maximum number observed in cattle and beefalo was 5 and 4, respectively. Importantly, when compared to cattle, 11% of beefalo spermatocytes exhibited chromosomes with structural defects and 9% were lacking a CO, both of which lead to improper chromosome segregation, and ultimately apoptosis and reduced fertility. While hybrid species and subspecies crosses have the potential to provide valuable phenotypic traits, understanding chromosomal differences will help resolve breeding difficulties. This research contributes valuable information towards understanding meiotic recombination in livestock, for use in both genetic predictions and selection strategies. Keywords: meiosis, cattle, sheep, beefalo, crossovers

Anna M Rodriguez, Kimberly Davenport, Benton Glaze, Stephanie McKay, Clare Gill, Brenda Murdoch

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Biology - Reproduction 1, , 934, 2018
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