Laboratory methods of PGD
The cells collected form the three-day-old embryo are most often tested using the method of fluorescent in situ hybridization (FISH). This molecular cytogenetic technique is suitable in case of an examination of aneuploidy of the embryos, determination of sex of the embryos or identification of the carrier of the structural aberrations. For the detection of a monogenous disease a genetic method known as the polymerase chain reaction (PCR) is used. The fluorescent in situ hybridization is based on the principle of hybridization of a short fluorescently labelled sequence of DNA (a so-called probe) with the corresponding sections of the target DNA sequence from the embryonic cells being examined. This hybridization result is deducted from with the assistance of a fluorescent microscope. Thus we obtain an overview of the number of copies of the selected section of DNA, representing a certain chromosome, in the nucleus of the examined embryonic cell. The polymerase chain reaction was developed in 1980’s and today it represents one of the most common tools of the molecular genetic diagnostics. The basis of this highly efficient method is in vitro synthesis of a selected section of DNA, which proceeds in many repeated cycles. As a result we obtain a large number of copies of the given section of DNA. This amplified fragment can subsequently be separated and visualized by means of electrophoresis. The most sensitive electrophoresis type is the so-called capillary electrophoresis, which we have for disposal in our laboratory. With the help of these methods it is also possible to analyse a very small quantity of DNA, thus also DNA contained in only one cell.