| Popis: |
A number of diseases are genetic, that is to say inherited (Milunsky, 1986). Some of these will manifest themselves early in childhood resulting in severe physical and mental handicap, and sometimes in the demise of the child before its teens. Many couples who carry such genetic diseases already have one affected child and are eager to take advantage of methods which will allow antenatal diagnosis of the condition during a subsequent pregnancy. However a number of women, whether for religious or personal reasons, cannot accept abortion of an affected pregnancy and would rather avail themselves of methods to diagnose the genetic disease prior to conception. The clinical and laboratory procedures for in vitro fertilisation (IVF) which were originally developed for the treatment of tubal infertility (Edwards et al., 1980), now enable diagnosis of genetic disorders before the pregnancy is established, thus obviating the need for repeated and often late therapeutic abortions (McLaren, 1985; Verlinsky et al., 1990b). This technique of preimplantation diagnosis requires the taking of a single cell or group of cells, from the egg or early cleavage stage embryo in vitro, as a biopsy on which a diagnostic test can be performed for the particular genetic lesion (Figure 4.1). Only those preimplantation embryos which have been found to be free of the particular genetic disease are selected for replacement into the woman’s uterus. Thus the couple can continue with the pregnancy safe in the knowledge that their baby will not be affected by the disease for which they are carriers. |
