A cytological and molecular analysis of cattle, bull clones and their offspring

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Hart, Ezra J.
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University of Guelph

To assess the impact of cloning by SCNT on the meiotic processes, we undertook a molecular and immunocytological comparison of bull clones and their offspring. This was the first assessment of recombination frequency in cattle meiosis and the first attempt to examine the effect of SCNT on recombination and the associated proteins, within any cloned species to date. The recombination profile of five normal bulls of proven fertility, two SCNT-derived bulls and four mature offspring of SCNT bulls were examined through immunocytology and showed that the mean number of crossing over events per spermatocyte for SCNT-derived bulls (43 ± 5SD, ranging from 35 to 56), and their offspring (46 ± 4SD, ranging from 37 to 58) was not significantly different from normal non clone bulls (42 ± 4 SD, ranging from 33 to 56). Additionally, initial results indicate that there is a similar level of recombination in female cattle to that of the male. The mRNA expression levels of the meiotic proteins SCP3 and MLH1 were also examined, using real time quantitative PCR (RT-PCR). Again, no significant difference was observed between groups in expression levels of either protein. Lastly telomere lengths were compared between groups and no significant difference was found. It would appear that the SCNT procedure has had no influence on the meiotic processes and reproductive health of animals produced by SCNT or their offspring.

cloning, SCNT, somatic cell nuclear transfer, meiotic processes, bull clones, offspring, recombination frequency, reproductive health