DNA index, genome size, and electronic nuclear volume of vertebrates from the Miami Metro Zoo

Abstract

BACKGROUND: Flow cytometry is a rapid and reliable method for measuring nuclear DNA content and genome size. Fluorochrome binding characteristics, sample preparation and differences in DNA condensation, and availability of binding sites can cause variations in results obtained. METHODS: Blood samples from 82 vertebrate species were collected in 10% dimethyl sulfoxide and stained with propidium iodide/hypotonic citrate or 4,6-diamidino-2-phenylindole dihydrochloride for analysis of DNA content and electronic nuclear volume (ENV). Trout red blood cells (TRBCs), human peripheral blood lymphocytes, and human buccal cavity cells were used as internal standards. RESULTS: Mean fluorescence channel (MFC) values of TRBC and buccal cavity cells used as internal standards were stable at 15 to 120 min of propidium iodide staining. TRBCs mixed with other cells especially human peripheral blood cells showed an increase in MFC. ENV and MCF values were less variable in different species of birds than in reptiles or mammals. Genome size based on use of buccal cavity cells as the internal standard showed a high degree of correlation with previous reports. CONCLUSIONS: Proper selection and use of internal standards and sample preparation are essential for reliable determination of DNA content and genome size in vertebrates by flow cytometry.