Genes and Behaviour
Process
Environmental
Regulatory genes
Environmental influences
turn genes on and off
Structural Genes
Enzyme production
Enzymes
Regulated biochemical reactions
Carbohydrates, fats & proteins
Physical (e.g. temp)
Cell metabolism
Carbohydrates, fats & proteins
Development of
nervous, skeletal &
endocrine systems
Environmental influences (e.g. visual input for
the development of the CNS)
Physiological mechanisms
Sensory perception, CNS processing,
Motor generation
Environmental influences(e.g. social environment)
BEHAVIOUR
Drosophila Courtship
Drosophila Courtship
fru gene – one in a hierarchy
Gene A affects
Gene B affects
Gene C
Drosophila Courtship
Transformer gene (tra)
Number of X
chromosomes
Affects fru
Effects on genes that build neural
circuitry and on sex determination
Group of fru expressing
neurons in males
Expressed in ~1.5% of neurons
But in all sensory neurons
involved in courtship
In females,
neurons die
Drosophila Courtship
Effects of fru gene are concentrated in certain sensory neurons
Mutants of fru gene
Methods for Studying Behavioural Genetics
1. Study of Mendelian Traits - Single Gene Effects
2. Inbreeding Studies
3. Artificial Selection - Quantitative Genetics
4. Induction of Mutations - Really Stupid Flies
A FEW GENETIC TERMS:
Pleiotropy - the situation in which a single gene has an effect on the
expression of two or more traits
Polygenic - the situation in which a two or more genes are responsible for
a single trait
Additive effects - When the combined effects of alleles at different loci
are equal to the sum of their individual effects.
Epistasis - The masking of the phenotypic effect of alleles at one
gene by alleles of another gene. A gene is said to be
epistatic when its presence suppresses the effect of a gene at
another locus.
1. Study of Mendelian Traits
INHERITANCE OF SONG PATTERNS IN CRICKETS
Teleogryllus commodus
Teleogryllus oceanicus
X
F1 hybrid
(BENTLEY, 1971)
1. Study of Mendelian Traits
INHERITANCE OF SONG PATTERNS IN CRICKETS
(BENTLEY, 1971)
Teleogryllus commodus
X
Teleogryllus oceanicus
X
F1 hybrid
T. commodus
X
F1 backcross
T. oceanicus
x
F1 backcross
1. Study of Mendelian Traits
Ruffs - Philomachus pugnax - (Lank et al, 1995)
MALES - 2 KINDS
Satellite
Independent
1. Study of Mendelian Traits
Ruffs - Philomachus pugnax - (Lank et al, 1995)
MALES - 2 KINDS
Satellite
Independent
- smaller
- larger
- don’t hold mating territories
- hold mating territories
- less colourful
- more colourful
- ca 16% of population
- ca 84% of population
1. Study of Mendelian Traits
Ruffs - Philomachus pugnax - (Lank et al, 1995)
MALES - 2 KINDS
Satellite
Independent
ss
SS or Ss
- controls mating behaviour, body size and plumage
Foulbrood in Honeybees
Under the control of two alleles
Foulbrood in Honeybees
Under the control of two alleles
u - for uncapping
Hygenic
r - removal
U - no uncapping
R - no removal
Female (uurr)
X
Male (UR)
All females - non-hygenic
(UuRr)
Non-
hygenic
Foulbrood in Honeybees
Now do various backcrosses F1 females to males
Genotype
U_R_
No
uncapping
*
u_r_
No
removal
Removal
*
*
u_R_
U_r_
Uncapping
*
*
*
*
*
2. Inbreeding
Inbred strains of Macropodus opercularis - Miklósi et al (1997)
Two strains - S and P
2. Inbreeding
Inbred strains of Macropodus opercularis - Miklósi et al (1997)
Young (larval) fish were tested for their response to a predator model
1. Fleeing
2. Backing
2. Inbreeding
Inbred strains of Macropodus opercularis - Miklósi et al (1997)
P strain
S strain
Frequency
of fleeing
Model with
eyes
Model with
no eyes
2. Inbreeding
Inbred strains of Macropodus opercularis - Miklósi et al (1997)
P strain
S strain
Frequency
of backing
Model with
eyes
Quantitative Genetics
1 allele
2 alleles
X alleles
For any trait:
Total variance = genetic variance + environmental
variance
Or
VT = VG + VE
V
G
Heritability =
VG + VE
2. Inbreeding to show the role of the environment
Using inbred strains – do reciprocal crosses
1) Strain A male x Strain B female
2) Strain B male x Strain A female
Offspring all with same genotype
If behaviour of F1(AxB) ≠ behaviour of F1(BxA)
- influence of parental environment
2. Inbreeding to show the role of the environment
-to detect postpartum maternal influences
CROSS-FOSTERING
Microtus pennsylvanicus
Meadow vole
Microtus ochrogaster
Prairie vole
Prairie vole
- more parental care from female
- male tends young
Meadow vole
- less parental care from female
- male does not tend young
McGuire(1988)
Cross fostering experiment
Meadow vole  raised by prairie vole parents
Meadow vole  raised by meadow vole parents (control)
Looked at parental care offered by cross-fostered offspring
If parental care is all genetic – should show no difference
Males
Females
Cross-fostered
meadow voles
Control
meadow voles
Offer more care
to own offspring
No difference in
care offered
Twin Studies
Inducing mutations
Normal Drosophila
- can learn to associate shock and odour
Inducing mutations
Mutant Drosophila
- dunce gene can’t learn to associate shock and odour
- On X-chromosome
Inducing mutations
Mutant Drosophila
- dunce gene can’t learn to associate shock and odour
Why??
Hypothesis 1: dunce mutant can’t smell
✖
Hypothesis 2: dunce mutant can’t feel shock
There is a problem in forming a memory
✖
Dunce and rutabaga genes - Drosophila
ATP
cAMP
Adenylyl
cyclase
cAMP phosphodiesterase
Binds and activates
PKA
activates
CREB
Turns on genes that cause changes
in structure and function of nerve
cells that govern memory
Artificial Selection - Drosophila geotaxis
Selection of positively and negatively
geotactic Drosophila
Breed together
Negatively geotactic
• •
• •
• ••
• •
•
Positively geotactic
Breed together
• •
••
• •
• ••
• •
•
• •
•
Artificial Selection - Drosophila geotaxis
Selection of
positively and negatively
geotactic Drosophila
Artificial selection
- mating speed in Drosophila
Fast maters
Control
First half of
maters
Slow maters
Second half of
maters
Repeat for 25 generations
Got three distinct lines
Fast - 3 mins
Control - 5 mins
Slow - 80 mins
Artificial Selection – Mus musculus nests (Lynch, 1980)
Hybridization experiments - Sokolowski
Sitter
Rover
P1
Sitter
Rover
Path length
Path length
Sitter
Rover
Path length
F1 x F1
Sitter
Rover
Path length
Hybridization
Alleles are forS and forR
Rovers are forRforR or forRforS
Sitters are forSforS
Hybridization Experiments - Lovebirds
Peach-faced
Fischer’s
Parent Offspring Regression
Activity scores with Drosophila
•
•
Offspring
•
•
•
• •
• • •
•
Slope = heritability
•
•
•
Mid-parent score (P1 + P2)
2
F. Comparative approach - Temperature selection in Peromyscus
Preferred Temperature
(Adults)
-5
0
5
10
15
What about genes that affect larger
collections of behavioural acts?
fosB gene in rats
Brown et al. 1996. A defect in nurturing in mice lacking the immediate early gene fosB. Cell 86: 297 - 309
fosB gene in rats
Normal rat
Nursing
Mutated fosB rat
Retrieving
Hypothesized action of fosB
Maternal behaviour
Odour activates
fosB gene in
preoptic
hypothalamus
Female rat
Odour of rat pups
Gene activation in hypothalamus
FosB mutant
Normal
fosB gene in rats
How does it work?
Possibilities
Pleiotropic effect of other genes
No retrieval
-lack spatial sense?
- normal maze running ability
No nursing
-poor mammary
development?
- normal mammary glands
Mammary Development in Rats
Normal
FosB mutant
fosB gene in rats
How does it work?
Possibilities
Pleiotropic effect of other genes
No retrieval
-lack spatial sense?
- normal maze running ability
No nursing
-poor mammary
development?
- normal mammary glands
-lack estrogen or
progesterone?
- normal hormone levels
-lack olfactory sense?
- normal olfaction
fosB gene in rats
Odour
Olfactory nerve
Activation of fosB genes in preoptic area
Other genes
Other genes
Other genes
Other genes
Other genes
Other genes
fosB is necessary but not sufficient to induce maternal behaviour
Other genes
So far – talked about the genetic contribution to a trait
Heritability =
VG
VG + VE
What about the environmental contribution?
Dominance Relationships of Cichlid Fish
S. Burmeister
Astatotilapia burtoni
Territory holders
Subordinate males
Burmeister et al 2005. PloS Bio. 3:363
Dominance Relationships of Cichlid Fish
Gonadotropin releasing hormone (GnRH)
- Encoded by GnRH gene
-effects on GnRH-releasing neurons in preoptic
area of hypothalamus
-dominant males – larger neurons due to
increased activity of GnRH gene
Dominance Relationships of Cichlid Fish
Non-territorial male
Wins some fights
Size increase
Sexual development
Colour change
Increase in GnRH activity
Increase in GnRH
receptors in pituitary
gland
Increase in GnRH
production
Dominance Relationships of Cichlid Fish
Subordinate male – grows quickly
Becomes dominant
Social stimuli
Inhibition of growth
hormone
Activation of gene
for somatostatin
Production of
somatostatin
Dominance Relationships of Cichlid Fish
If a dominant male is
removed (predation)
Loss of social input
Activation of immediate
early gene - erg-I
Changes in fertility
(1 week)
Changes in colour and
aggressive behaviour
(minutes)
Triggers changes in
GnRH
Dominance Relationships of Cichlid Fish
If a dominant male is
removed (predation)
Loss of social input
Activation of immediate
early gene - erg-I
Development of subordinate
Activity is greatest in
areas of brain rich in
GnRH-releasing neurons
Erg-I codes for proteins that
regulate activity of GnRH