Embryo sexing

The sexing technique is based on the chromosomic difference between embryos of different sex, the presence or absence of the Y chromosome (the male embryos carry the Y chromosome while the female embryos do not). In order to highlight this difference a small group of cells of the embryo is removed by using a microblade (Fig.1). The DNA contained in these cells is amplified with a procedure called PCR (Polymerase Chain Reaction) which allows to find out the presence or absence of the male chromosome Y. Together with the signal for the Y chromosome, a second signal of control is obtained for all samples analysed independently from the sex. These signals are visible as fluorescent bands after electrophoresis of the DNA samples in an agarose gel (Fig.2). The interpretation of the result is very simple: the presence of a single band indicates that the biopsy has been taken from a female embryo while the presence of two bands indicates that the biopsy has been taken from a male embryo. The sexing procedure is accurate at 97%. The sexed embryos can be successfully frozen exactly as the non sexed embryos. 

Fig 1: Embryo Biopsy sequence. With the aid of a microblade, a small group of cells is separated from the rest of the embryo. The DNA of these cells is used for sex determination.

 

Fig 2: Electrophoresis of embryonic DNA in agarose gel. The samples with two visible fluorescent bands correspond to biopsy collected from male embryos; the samples in which only one band is visible correspond to biopsies collected from female embryos.

The embryo sexing service

The embryo sexing service started in 1997, since then over 2000 LTR embryos have been sexed. This service is also available for embryos produced by third parties.