Genome quantitation and analysis in fishes
Abstract
The genome sizes of extant fishes reflect the history of evolution in fishes and provide information about mechanisms of fish genome change. DNA in erythrocytes of 25 species and 5 hybrids was quantitated by flow cytometry. Most species studied were indigenous to North America. The genome size in seven of the eight North American Acipenseriformes ranged from 4.6 to 13.1 picograms. Three distinct groupings of genome size occurred in an approximately 1:2:3 ratio, indicating ploidy differences between groups. Species with the smallest genomes are considered tetraploids of some ancestral fish and therefore, 4C. The intermediate genome size consists of octaploid (8C)-derived species and the largest genome was a dodecaploid (12C)-derived species. Spontaneous triploids (3N) of the lake sturgeon, Acipenser fulvescens, and the Gulf of Mexico sturgeon, A. oxyrhynchus desotoi, indicate that polyploidization mechanisms continue in the Acipenseriformes today. The mean genome size of white sturgeon, A. transmontanus, from Idaho was found to be significantly smaller (P $<$.05) than that of white sturgeon from California and Washington. In the 25 species studied which include representatives of Chondrostei, Holostei, and Teleostei; genome size ranged from 1.6 to 13.1 picograms with progressively smaller genome size in more modern fishes. A generally accepted hypothesis is that all fishes are derived from a common tetraploid ancestor. Evidence of additional tetraploid events followed by diploidization were seen in salmonids, carp, and goldfish. In hybrids of Stizostedion and the Morone species, genome sizes were greater (P $<$.05) than the mean value of the parents. The genome size of reciprocal hybrids of the loach (Misgurnus sp.) was not different than the mean of the parents. This data indicates that in some instances hybridization results in DNA amplification. The analysis of genome size indicates that both polyploidization and hybridization have been factors in genetic evolution in fish.
Degree
Ph.D.
Advisors
Bidwell, Purdue University.
Subject Area
Genetics|Zoology
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