Behavior: Genes and Behavior

• Relatively rare (as usually more than one gene involved in behavior) but relatively easy to study
• Eg. hygienic and non-hygienic honey bees: bacteria (American foul brood) that attacks bee larvae.  Hygienic colonies worker bees will uncap a cell in the colony if dead larva or pups are remove the corpse, non-hygienic colonies workers do not.

• "knockout" - a gene is removed or rendered inactive
• "knockin" a novel gene is inserted
• "conditional" the promoter for a gene is altered so that it can be switched on or of by the experimenter

• Most phenotypic characters are not associated with a specific gene but are the result of numerous genes interacting (polygenic)
• These effects are far harder to study, because many genes may have a small but important effect on phenotype
• Do not follow Medalian laws of inheritance
• Lots of work currently being done on quantitative genomics to id important genes for growth, development and disease susceptibility

• Allele has more than one effect on the phenotype
• Yellow allele in Drosophila: slower at matting, yellow strips on the body
• Norm rather than the exception
• Change in one enzyme likely to affect several pathways and phenotypic characters

• Approaches to demonstrate genetic effects on Behaviour all involve linking behavior variation to genetic differences
• 1. using "natural" behavioral variation
• 2. using selective breeding
• 3. Using strain differences

• Interbreed closely related species with different patterns of behavior to study genetic influences of behavior
• e.g. Nest-building behavior in love birds

• Separate behavioral variants from within a population
• Select specific individuals to breed and repeat selection process in each generation (temperament)
• Behavioral differences that respond to selective breeding must be due at least in part to the differences in the genotype

• Temperament (calm -  reactive) in cattle is heritable
• Heritability of 0.4-0.5 have been reported
• Angus more temperamental than Herefords
• Braham cross more agitated during restraint than shorthorns

Process by which a population of animals become adapted to man and the captive environment by genetic changes occurring over generations and environmentally-induced developmental events reoccurring during each generation

• Inbreeding
• Genetic drift
• Selection: artificial, natural, relaxation of natural selection

• Create random changes in gene frequency
• Small captive populations
• Decreased genetic variabilityy
• "inbreeding depression" - lowering fitness of vigor due to inbreeding: egg hatchability, clutch size, milk yield, litter size
• Increased risk of genetic disease

• Certain alleles become randomly fixed or lost
• Decrease genetic variability
• Becomes more severe and more important the smaller the breeding population is
• "Founder Effect" - When a population is bred from a few originators, genetic drift can be exceedingly severe, and alleles from one or two founders can dominate the resulting population: probably a common component of genetic disease in inbred populations, Known cause of behavior problems in show dogs.

• Behavioral problems
• Physiological problems
• Immunological problems
• Production diseases: diseases caused by systems of management, feeding and breeding of high producing strains of animals

• Selection for increase milk production
• Lower energy balance in high producers
• Higher incidence of metabolic disorders
• More days open
• Longer calving interval
• More service/conception
• More digestive problems
• More leg injuries

• Over-selection for desired traits can lead to pleiotropic selection for undesired traits
• Broiler chickens have been intensively selected for breast muscle mass growth, and muscle, carcass weight ratio: rapid growth, altered feeding behavior; altered weight distribution affects gait; growth of skeleton and internal organs does not keep up

• Reduced cardiopulmonary capacity
• Cannot withstand much physical exertion, prone to stress-induced mortality as they age...
• ...so that breeding birds must be heavily food restricted in order to survive to sexual maturity
• Bone weaknesses, and diseases of - and injuries to - the legs
• A small proportion of birds may become too lame to reach food and water

• Behavior is easily pleiotropically selected
• eg. selection for rapid growth of individuals can also lead to selection for aggression
• When these individuals are housed together aggression may be so severe that it hinders the average growth seen in the group

• Lots of work happening right now
• Gene for serotonin receptor HTR2C and feather damage
• SNPs (single nucleotide polymorphisms) in a number of genes mediation HPA (hypothalamic-pituitary adrenal) axis affects vasopressin receptor 1B and glucocorticoid receptors

• Molecular biology, gene editing
• What traditionally (be selective breeding) takes 8 generations (24 years in cows) can now be accomplished in a single generation by gene editing.
• We demonstrated that a sequence associated with horns in dairy cattle could be converted to a natural beef cattle variant that is hornless, providing a strategy to improve animal welfare by genetic instead of physical or chemical dehorning