Fig. 6. RT-PCR detection of mRNA for SIT1 (Slc6a20a) and PROT (Slc6a7). PCR was performed on cDNA from mouse MII eggs (MII), 1-cell (1c), 2-cell (2c), 4-cell (4c), 8-cell (8c), morula (M) and blastocyst (B) stage embryos, with kidney (K) as a positive control to indicate the position of amplicon (the band intensity from kidney relative to those of the embryos is of no physiological relevance). Slc6a20a and Slc6a7 mRNAs were most strongly detected in MII eggs and 1-cell embryos. H2afz was used as a positive control for the presence of cDNA. The expected amplicon sizes (bp) are indicated on the left and by arrows in each marker lane (m, a 100-bp ladder, the largest visible band of which is sized). Only portions of each gel are shown, but no other bands were visible below or above. The example shown is one of two independently collected sets of RNA. In the other, intense bands were evident at the MII and 1-cell stages as shown here, but faint bands were also visible at other stages.