Quantitative aspect of gene expression analysis in mammalian oocytes and embryos.

In vitro produced embryos, due to their lower developmental potential when compared to the in vivo derived counterparts, have been currently subjected to an intensive scientific investigation. Qualitative as well as quantitative analyses of gene expression (reverse transcription-polymerase chain reaction; RT-PCR) belong to the powerful tools providing a wide spectrum of data on the quality of oocytes and embryos. The main research areas in this topic concern the following categories: oocyte quality, developmental competence of in vitro produced (IVP) embryos also with regard to their sex, embryo metabolism, gene expression levels, embryo manipulation and cloning. There are many methods that have been applied to study gene expression, but only some of them meet the requirement of analysing small cell samples which usually is the case with oocytes or early embryos. This paper deals with the description of the current methods commonly used for quantitative gene expression in mammalian oocytes and preimplantation embryos with a special attention paid to the real time PCR.