Proximate causes Interaction among gene/environment/ development persist and change over entire lifetime of animal We’re simplifying by focusing the “straight line” interactions for now

Behavioral Genetics Single gene effect - Drosophila sp. V T = V G + V E + V I V I = V G x V E Inbreeding - homogeneous strain - e.g. rearing condition (V G = 0, V T = V E ) Strain difference (V E = 0, V T = V G )

Hybridization - love birds, hygienic vs. unhygienic bees, cricket song Cross-fostering - e.g. cockatoo-reared galah – galah begging call, alarm call, – cockatoo contact call, slow wingbeat, food

Heritability Degree of genetic determination ratio of genetic variation in a behavior trait GD = V G /( V G + V E + V I ) Cross inbred strains and measure behavioral variation

V E = ( )/3 = 285 V G = = 180 GD = V G / V T = 180/465 = 0.39

Realized heritability, h r 2 : a measure of the response of a trait to selection Measure differences in behavioral traits between base stock and selected breeding parents (S), and between base stock and offspring (R) Selection differential, S Response to selection, R h r 2 =R/S

TREES 6(8): , 1991 Genetic control of migratory behavior When to migrate? Migratory pop. x Resident pop. => 40% of F1 migratory The migratory restlessness may change by selective breeding

How far? ---Long distance x Short distance => intermediate distance What direction? ---Resident x Exclusive migrant =>F1 migrant w/ parent direction ---SE migrant x SW migrant =>intermediate ---Species change direction during migration. Captive ones show same behavior

Other migratory traits: ---morphological features ---seasonal change in feeding rate, food and habit preference, activity pattern

Group size preference Proc. Nat. Acad. Sci. USA 97: Parent – offspring regression Group size of individual cliff swallow (Petrochelidon pyrrhonota) ~ parents Foster-raring individual ~ biological parents

Naive animal - e.g. garter snakes and slug Mutation Twin studies – identical (monozygotic) twins – fraternal (dizygotic) twins Mosaic Quantitative Trait Locus Analysis (QLT)

Towards behavioral genomics Science 291: , 2001 Single genes do not determine most human behavior Nearly all behaviors that have been studied showed moderate to high heritability Environmental factors make people different from, rather than similar to, their relatives

Information and techniques generated by the human genome sequence will help locate and identify genes involved in behavior Problems – Detect genes of a linkage with large enough effects – Most valid diagnostic schemes for genetic research

A greatly improved map of human genome sequence helps improve allelic association studies to locate QTLs To ID the effects of QTLs – Bottom-up: functional genomics and proteomics – Top-down: behavioral genomics – Genome sequences of other organisms

Future perspectives – Understanding the neurobiological basis of individual (behavioral) differences and a better grasp of the etiology of diseases – Discovery of new and more specific drug treatments Limitation – Gene-environment interplay – Distribution of effective sizes of QTLs

Molecular techniques Transgenic Knockout Gene mapping and association Protein electrophoresis DNA fingerprinting

Per gene and song pattern Observation – – In both D. melanogaster and D. simulans wildtypes, difference in per alleles ~ differences in male songs (pleiotropy). – Wildtype per alleles differ in different species Hypothesis – Intraspecific differences in song are caused by differences in the per alleles

Building a brainier mouse (Sci. Am , 2000) Molecular basis of learning and memory Hebb’s learning rule – a memory is produced when 2 connected neurons are active simultaneously in a way that strengthens the synapse LTP – Long-term potentiation vs. LTD – Long-term depression of synaptic connection in hippocampus

NMDA receptors require 2 signals: binding of neurotransmitter glutamate, membrane depolarization Dumb mouse – NMDA lack NR1 subunit in CA1 region, impairment in spatial memory and other task Young animals produce NR2B, old animals more NR2A in NMDA, NR2B stays longer than NR2A

Smart mouse – extra copies of NR2B Test 1. Recognition of objects: smart mice explore only new objects, normal mice explore both old & new, remember objects 4~5 times longer Test 2. Remember fear longer Test 3. Fear extinction learning faster

Test 4. Morris water maze, finding submerged platform in milky water – need analytical skill, learning and memory, ability to form strategies Learning and memory enhance problem-solving, but intelligence has many aspects