Abstract
Methods for collecting cells in metaphase and spreading chromosomes (hypotonic treatment) were investigated in 2-cell bovine embryos derived from in vitro fer-tilization and the sex ratio was studied. The embryos were exposed to 0.08 or 0.16 μg/ml of vinblastin-podophyllotoxin (V-P) for 12 hr at 39°C before being treated with 0.75-1.0% of sodium citrate solution for 15 to 60 min. The exposure to 0.08 μg/ml V-P yielded analyzable metaphases in 69.1% of the embryos prepared, which was contrasted with 42.9% in the exposure to 0.04 μg/ml colcemid for 4 hr. A hypotonic treatment with 1.0% sodium citrate for 60 min was recommended to obtain a high quality of metaphase spread. Chromosomal sexing was made for 61 embryos with a sex ratio of 63.9% males.
