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genetic variation originally present in broodstocks may have been lost. An important goal of all broodstocks programs should be to prevent further loss of genetic variation. All broodstock managers should be encouraged to promote a better understanding of genetic principles and practices as they relate to broodstock management. The following information provided in this section is intended to help accomplish these goals. Causes of the Loss of Genetic Variation 1. Genetic Drift Genetic drift is the random genetic change that occurs from one generation to the next if only a limited number of parents are available to contribute genetic information to the succeeding generation. The result of genetic drift is that the genetic make-up of each successive generation is less variable than that of the- preceding one. Genetic drift results in the loss of alleles. When a very limited number of parents are used in any given generation, an extreme case of genetic drift may result. This situation is commonly referred to as a "bottleneck". When a bottleneck occurs, a considerable portion of the genetic variability present may be lost within a single generation. The effect of using-small numbers of parents to initiate new populations are commonly called "founder effects". 2.` Inbreedingt Inbreeding is the mating of related individuals.- The more closely related certain individuals are, the less variable they are and the less variable their offspring. In small populations, inbreeding is often a problem as the odds of related individuals mating is increased (1). 3. Intentional Selection Genetic selection for a specific trait or characteristic reduces genetic variation at not only the targeted gene loci, but at all loci. If the population in question is small, the odds of selecting related individuals is even greater than it might otherwise be. Intentional selection can increase the rate of both genetic drift-and inbreeding. 1-2