A rapid, highly reproducible and sensitive technique has been successfully developed for sexing the cow embryos, by method of polymerase chain reaction (PCR) against the amelogenin (bAML) genes located on both X- and Y-chromosomes of the Holstein dairy cattle. Results from DNA sequence analysis showed that there was only 45% homology between the intron 5 of AMLX and AMLY genes. Based on these sequences a pair of sex-specific primers, pbAML5XY(+) and pbAML5XY (-), were designed allowing to amplify a single fragment of 476-bp from the female cattle and two fragments of 476-bp and 341-bp from the male ones, respectively. The most important feature is that the precise sensitivity of sex-determination was confirmed to be reached as minimum template as trace amount of genomic DNA content in either a single lymphocyte or a single blastomere isolated from cow embryo at day-6 to day-7. Moreover, neither those of complicated procedures for purifying the DNA prior the PCR nor any extra pair of primers for serving as internal control is thought to be essential and the sex-determination of over hundred embryos can be completed at once within 4hrs.
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