Localizing the GYPA gene by FISH. FISH was performed using the 159F4 BAC probe to examine the chromosomal location of the GYPA gene, which encodes the hGPA protein. As a positive control, the probe hybridized to human chromosome 4 (A), and, as a negative control, the probe did not hybridize to any wild-type FVB/NJ mouse chromosome (B). However, the probe did hybridize to one chromosome from hemizygous hGPA-Tg mice (C-D). The locations of hybridization are indicated by white arrows.