Transcript The genetic basis of behavior

Biology 312
Lecture 3: Genetic basis of
behavior
Lecture outline
1. Overview


Genes affect behavior through gene
products
Individual genes can have profound effects
on individual behaviors
2. “Organism-level” methods for
determining relative roles of genes
vs. environment
Genes affect behavior through
gene products

Examples of “gene products” involved in
behavior
 Protein
hormones
 Channels in neurons (Na+ channels, for ex.)
 Receptors
 Nerve growth factor
 Structural proteins (such as muscle)
 Enzymes involved in metabolic pathways that
synthesize key substances such as neurotransmitters,
steroid hormones, eye pigments, etc…
 Regulatory proteins that turn other genes on and off

Any given behavior requires many gene
products
Individual genes can have
profound effects

Example: “Pawn” Paramecium
Mutation:
Pawn allele codes for defective
Ca++ channels

Ca++ entry is necessary for reversal of ciliary beat
Behavioral
impact: Paramecium cannot back
up

Example: song learning in canaries
Single
gene (“zenk”) is turned on in young
males with exposure to the song of its own
species but not others

Suggests that “zenk” plays a role in song learning
“Zenk” activity in the forebrains
of songbirds
Methods: Relative roles of genes vs.
environment in a behavior

Inbreeding
 What
are inbred strains?
 How are inbred strains used to determine genetic basis
of behavior?

Example: Anti-predator response of paradise fish

Inbreeding (cont.)
 How
are inbred strains used to determine the
environmental basis of behavior?

Expose individuals of the same strain to different environments


Differences among habitats will be easier to observe (since
genetic differences have been minimized)
Ex: Maze-bright vs. maze-dull mice in restricted vs. enriched
environment
Methods: Relative roles of genes vs.
environment in a behavior (cont.)

Artificial selection
 What

is artificial selection?
How does it differ from inbreeding?

Breeding based on relationship (inbreeding) vs. breeding
based on behavior (artificial selection)
 How
is this technique used to determine the genetic
basis of behavior?

Example: Attempting to create races of smart and dull
mice based on their maze performance
 How
is this technique used to determine role of the
environment?

See previous example (same as for inbred strains)
Methods: Relative roles of genes vs.
environment in a behavior (cont.)

Hybridization
 What
are hybrids?
 How is this technique used to determine the genetic
basis of behavior?

“Whenever the pattern of inheritance is always the same, a
genetic basis for that behavior is implied.”

 Example:

Hoy and Paul, 1973
Cricket song patterns
Do male hybrids of two closely-related cricket species sing
a characteristic song?
Song patterns in hybrids of the
cricket genus Teleogryllus