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Laboratory Animal Science (Subject) / Genetics (Lesson)

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• Aim of lab animal breeding Standardizing the genetic influenceson the target characters inanimal experiments
• Target character groups Monogenic: The phenotype is caused by a single gene or a few genes;the environment does not matter significantly Polygenic The phenotype is caused by a (more or less large) number of genes; environmental effects may play a significant role
• Define Heritability Coefficient h² Relation between the genetic variance and the total varianceof a given characterThe coefficient value differs theoretically between0% (no genetic influence) and100% (monogenetic inheritance, no environmental effects) (generally by estimating the similarity between relatives)- Comparison of full-sib groups- Comparison of different inbred strains- Comparison of parents/offspring
• The three breeding strategies Maximum homozygosity --> Inbreeding Repeatable heterozygosity --> Cross-Breeding Steady heterozygosity --> Outbreeding
• Concept, definition and characteristics of inbred Strains Concept: Generation and preservation of genetic homozygosityDefinition: A minimum of 20 consecutive generations of brother x sister matingFor experimental use animals of F>>50 isrecommendedCharacteristics: The individual genotype is highly repeatableThe phenotypical variation depends on strain and character; only caused by environmental factorsThe results are valid for individuals and samples but first of all restricted to the specific strain in use Additional undesired substrains can fevelop - avoid this  BY Substitution of the own breeders by original animals of the corresponding commercial breeder at least every 10th generation.
• Concept, definition and characteristics of outbreed stocks Concept: Preservation of an established genetic variabilityDefinition: Closed breeding colony with minimized increase of inbreeding by application of rotation systems-Targets: the genetic pool of a stock is mixed up in a controlled fashion thereby balancing the distribution of the genotypes of the different families Characteristics: The individual genotype is not repeatableThe genotype distribution is highly repeatableThe phenotypical variation depends on the genes and the environmentThe size of variation is stock- and character specificThe results are valid only for representative samples not for individuals - Minimizing the relationship among animals- Minimizing the genetic drift- High performance of repeating the genotype frequencies andcharacter distribution within representative samples

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