Sex-linked diseases are caused by mutations in genes carried on the sex chromosomes. X-linked diseases are far more common that Y-linked diseases due to the fact that there are many more genes on the X-chromosome than the Y-chromosome. X-linked diseases are inherited from a carrier mother or from an affected father. Each son born to a carrier mother has a 50% chance of inheriting the X chromosome carrying the mutant allele.

FISH testing is offered at Unistel and is the technique of choice to determine the sex of embryos, however, it cannot discriminate between normal and affected male embryos or between normal and carrier female embryos.

Sex selection for a non-medical reason is unacceptable and illegal in South Africa. (Tissue Act 2012)

Another option is to select for embryos that are gentically normal for the sex-linked disorder.  In this instance, gender is not tested.  The defective gene is examined using PCR or karyomapping.

   Blastomere indicating a female complement. 








Please do not hesitate to contact the PGD Laboratory with any questions at +27 21 938 9213.