Comparison of the reassociation and hybridization properties of the DNAs for several species of fish

• Main Author: Gharrett, Anthony John
• Other Authors: Simon, Raymons C., Oregon State University. Graduate School
• Format: Doctoral or Postdoctoral Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: DNA; Thymallus arcticus
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/rb68xg61f

The genome composition and DNA base sequence homologies of several diverse species of fish were examined. The fishes were characterized from spectrophotometric studies of reassociation and hybridization of their DNAs and from the thermal stabilities of hybrid duplexes. Spectrophotometric studies indicated that repeated sequences comprise 35-40% of the genomes of starry flounder (Platichthys stellatus), ling cod (Ophiodon elongatus), and buffalo sculpin (Enophrys bison), and approximately 60% of the genomes of the salmonids (Salmo gairdneri, Oncorhynchus tshawytscha, Prosopium williamsoni, and Thymallus arcticus) and Pacific lamprey (Entosphenus tridentatus). The information content was relatively high in the steelhead ( Salmo gairdneri), 1.6 x 10⁹ base pairs, and lamprey, 2.3 x 10⁹base pairs, as compared to 0. 75 x 10⁹ in starry flounder. Hybridization studies indicate that closely related species share substantial base sequence similarities while distantly related fish share few or none. Hydroxyapatite chromatography was used for examining the thermal stabilities of DNA hybrids. This technique provided a means for separating closely related species, such as the salmonids. It was concluded that the specialization in fishes is accompanied by a reduction in information content and a decrease in repeatedness in their genomes. These observations are consistent with the loss of structural components and decrease in plasticity generally accompanying specialization. Quantitative differences were found in the base sequences of closely related species and, although differences between populations and races were not resolved, the data suggest that with sufficient refinement of the methodology, such separations might be made.