Biology 312Biology 312

Lecture 3: Genetic basis of Lecture 3: Genetic basis of behaviorbehavior

Lecture outlineLecture outline

1.1. OverviewOverview Genes affect behavior through gene Genes affect behavior through gene

productsproducts Individual genes can have profound effects Individual genes can have profound effects

on individual behaviorson individual behaviors

2.2. ““Organism-level” methods for Organism-level” methods for determining relative roles of genes determining relative roles of genes vs. environmentvs. environment

Genes affect behavior through Genes affect behavior through gene productsgene products

Examples of “gene products” involved in Examples of “gene products” involved in behaviorbehavior Protein hormonesProtein hormones Channels in neurons (Na+ channels, for ex.)Channels in neurons (Na+ channels, for ex.) ReceptorsReceptors Nerve growth factorNerve growth factor Structural proteins (such as muscle)Structural proteins (such as muscle) Enzymes involved in metabolic pathways that Enzymes involved in metabolic pathways that

synthesize key substances such as neurotransmitters, synthesize key substances such as neurotransmitters, steroid hormones, eye pigments, etc…steroid hormones, eye pigments, etc…

Regulatory proteins that turn other genes on and offRegulatory proteins that turn other genes on and off Any given behavior requires many gene Any given behavior requires many gene

productsproducts

Individual genes can have Individual genes can have profound effectsprofound effects

Example: “Pawn” Example: “Pawn” ParameciumParameciumMutation: Pawn allele codes for defective CaMutation: Pawn allele codes for defective Ca++

++ channels channels CaCa++++ entry is necessary for reversal of ciliary beat entry is necessary for reversal of ciliary beat

Behavioral impact: Behavioral impact: ParameciumParamecium cannot back cannot back upup

Example: song learning in canariesExample: song learning in canariesSingle gene (“zenk”) is turned on in young Single gene (“zenk”) is turned on in young

males with exposure to the song of its own males with exposure to the song of its own species but not othersspecies but not others Suggests that “zenk” plays a role in song learningSuggests that “zenk” plays a role in song learning

““Zenk” activity in the forebrains Zenk” activity in the forebrains of songbirdsof songbirds

Methods: Relative roles of genes vs. Methods: Relative roles of genes vs. environment in a behaviorenvironment in a behavior

InbreedingInbreeding What are inbred strains?What are inbred strains? How are inbred strains used to determine genetic basis How are inbred strains used to determine genetic basis

of behavior?of behavior? Example: Anti-predator response of paradise fishExample: Anti-predator response of paradise fish

Inbreeding (cont.)Inbreeding (cont.) How are inbred strains used to determine the How are inbred strains used to determine the

environmental basis of behavior?environmental basis of behavior? Expose individuals of the same strain to different environmentsExpose individuals of the same strain to different environments

Differences among habitats will be easier to observe (since Differences among habitats will be easier to observe (since genetic differences have been minimized)genetic differences have been minimized)

Ex: Maze-bright vs. maze-dull mice in restricted vs. enriched Ex: Maze-bright vs. maze-dull mice in restricted vs. enriched environmentenvironment

Methods: Relative roles of genes vs. Methods: Relative roles of genes vs. environment in a behavior (cont.)environment in a behavior (cont.)

Artificial selectionArtificial selection What is artificial selection?What is artificial selection?

How does it differ from inbreeding?How does it differ from inbreeding? Breeding based on relationship (inbreeding) vs. breeding Breeding based on relationship (inbreeding) vs. breeding

based on behavior (artificial selection)based on behavior (artificial selection)

How is this technique used to determine the genetic How is this technique used to determine the genetic basis of behavior?basis of behavior?

Example: Attempting to create races of smart and dull Example: Attempting to create races of smart and dull mice based on their maze performancemice based on their maze performance

How is this technique used to determine role of the How is this technique used to determine role of the environment?environment?

See previous example (same as for inbred strains)See previous example (same as for inbred strains)

Methods: Relative roles of genes vs. Methods: Relative roles of genes vs. environment in a behavior (cont.)environment in a behavior (cont.)

HybridizationHybridization What are hybrids?What are hybrids? How is this technique used to determine the genetic How is this technique used to determine the genetic

basis of behavior?basis of behavior? ““Whenever the pattern of inheritance is always the same, a Whenever the pattern of inheritance is always the same, a

genetic basis for that behavior is implied.” genetic basis for that behavior is implied.” Hoy and Paul, 1973Hoy and Paul, 1973

Example: Cricket song patternsExample: Cricket song patterns Do male hybrids of two closely-related cricket species sing Do male hybrids of two closely-related cricket species sing

a characteristic song?a characteristic song?

Song patterns in hybrids of the Song patterns in hybrids of the cricket genus cricket genus TeleogryllusTeleogryllus