154 LOCALIZATION BY IN SITU HYBRIDIZATION OF DNA PROBES WITH TIGHT LINKAGE TO THE LOCUS FOR THE CYSTIC FIBROSIS MUTATION

Abstract

Probes 7C22 and pJ3.11 known to be closely linked to the cystic fibrosis locus were made available to us by Prof. Williamson, London. In situ hybridizations were carried out on metaphase preparations of lymphocytes from a patient having an apparent deletion in band q22 of one of the chromosomes 7, but no CF. The site and number of grains were scored for the normal and the deleted homologue. The majority of the grains resulting from hybridization with 7C22 were found in the region q22-qter, with a clustering at the distal part of band 31 and at band 32. For pJ3.11 most of the grains were in the region q31-qter. The normal homologue was more frequently labelled than the deleted one. This difference might be due to random variation, although alternatively structural chromosome aberrations other than deletion might be involved in this patient. In summary, our preliminary results suggest the distal half of the long arm of chromosome 7 to be the location of these probes. Our studies are now being extended to some other probes linked to the cystic fibrosis locus.