Topic 3: Behavioral GeneticsSeveral lines of evidence prove that many if not most behaviors have at least some genetic basis to them. The question in Behavioral Genetics is: How much of a behavior is the result of Genetics (“Nature”) vs. Experience or Learning (“Nurture”)?Interactional Effects: Phenotypic outcomes that are influenced by both the alleles inherited from parents and the environment in which the animal is raised. (Remember that a “Behavioral Phenotype” will include learned behaviors acquired during an animal’s lifetime.)Mendelian genetics studies showed that behaviors can be analyzed similarly to physical or anatomical characteristics. Examples: Lovebird nest building behavior, Honeybee response to American Foulbrood infections.Deliberately induced mutations can be expressed as behavioral deficits or modifications. This is an early attempt to examine gene/behavior interactions and not very efficient.Knockout studies are a modern technique to assess single gene effects on behavior after particular portions of the genome have been identified by QTL. However, the many complex steps involved in the gene to behavior sequence must be considered when establishing the “cause” of a behavior. Although we assume that most behaviors are polygenic, the fosB mutant mouse example shows how disruption at a single gene locus can have profound effects on complex behaviors. Pleiotropy and epistasis are also factors that can complicate the gene/behavior interaction.Because we automatically assume that behaviors are polygenic (which can be shown by a Gaussian distribution), it makes an examination of gene/behavior interactions very complex. Cross-fostering and adoption/twin studies are “low-tech” ways of teasing apart the effects of genes and environment on behaviors. One of the best examples of cross-fostering is Mock’s study of Great Egrets and Great Blue Herons.Behavior: SiblicideEnvironmental difference: amount of food provided by parents.Example: Human adoption studies show that some measurements of verbal ability seem to be genetically influenced, based on correlations between children and biological parents.Heritability measurements can give us a quantitative idea of how strongly a phenotypic trait is influenced by genes. Heritability scores are always reported between 0 (no genetic influence) and 1 (phenotypic trait is completely the result of genes). Interactional traits (which we assume means most behaviors) are going to be some number 0<Heritability<1.Broad sense heritability is the proportion of variance attributable to genetic variance. The example was the foraging behavior of mice.Narrow sense heritability is the portion of genetic variance that is accessible to natural selection. This type of heritability measurement is particularly valuable to humans interested in applying artificial selection pressures in the process of domestication. The example was Longhorn horn length as described by Dr. David Hillis on his Double Helix Ranch website. Other measurements of narrow sense heritability in cattle are in the second to last paragraph. Dogs have also been examined for the heritability of behavioral