An Analysis of the Observed Heterozygosity of Lake Trout

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An analysis of the observed heterozygosity of Lake Trout populations from three lakes: Devil, Eagle, and Loughborough, inferred from microsatellite genotypes.

Abstract:
This study was undertaken in order to compare the heterozygosity of three Lake Trout populations at various loci. Samples of twenty-five Lake Trout were collected from three lakes: Devil, Eagle and Loughborough, all three of which are situated north of Kingston, Ontario. An autoradiograph was used to analyze the genotypes of the individuals at six different loci of microsatellites, which are repeat sequences in the DNA that are neutral and do not code for proteins. This data was used to compare the genetic diversity of the three different trout populations. Numerical values for observed heterozygosity (Ho) were then generated using the data and the Doh heterozygosity calculator. The results have indicated that the mean heterozygosity in respect of Devil Lake trout was significantly greater than that of the trout in Eagle Lake (p=2.89E-7) as well as that of Loughborough Lake (p=1.44E-19). Furthermore, the mean heterozygosity for Eagle Lake trout was significantly greater than that of Loughborough Lake (p=2.52E-6). This may be due to the fact that natural selection acts as a force to cause inbreeding to eliminate harmful genes causing low heterozygosity in a population. In addition, human and natural effects occurring in the lakes, for example, fishing and water temperature may cause differences in heterozygosity. Understanding and using these findings may help with sustaining fish populations.

Introduction:
Heterozygosity is the measure of the genetic variation in a population at a particular gene locus. Genetic variation within a population is important in maintaining or increasing the fitness of members in the population and ultimately the survival of the species. Fitness describes the capability of an individual species of a certain genotype to reproduce, and is usually equal to the proportion of the individual's genes in all the genes of the next generation. A positive correlation was found between the heterozygosity at the loci and the fitness (survival and maturation) of the fish, suggesting that heterozygosity is advantageous (Pujolar et al. 2005). A heterozygote advantage describes the case in which the heterozygote genotype has a higher relative fitness than either the homozygote dominant or homozygote recessive genotype. An individual's fitness is manifested through its phenotype, and the phenotype may be affected by both genes and environmental characteristics. One such characteristic that was observed to possibly have an effect on levels of heterozygosity in a population was the area in which the population lives. In an experiment conducted by Rowe et al. (1999) the heterozygosity of various populations of Natterjack Toads (Bufo calamita) found in several areas were compared, ultimately discovering a lower heterozygosity in a population that is isolated from others. Volckaert and Zouros (1989) conducted a study to measure genetic diversity levels in scallops (Placopecten magellanicus) and discovered levels of heterozygosity to be highest as age increased. Ferguson (1990) found similar information that affects diversity among rainbow trout (Oncorhynchus mykiss) and concluded that heterozygosity levels were proven to have a direct relationship between the sex, size and age of the fish. There are many factors that may affect the genetic diversity of a population. In particular, various events and environmental characteristics may affect the genetic diversity of Lake Trout. One factor may include fishing. This activity may cause the population of the fish to decrease at an unstable rate, thus this study will be undertaken to determine the many factors that may contribute influences to the genetic diversity of Lake Trout in three lakes: Devil, Eagle and Loughborough Lake. Using six microsatellite loci from 25 Lake Trout from...
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