Genes and Behaviour. Process Environmental Regulatory genes Environmental influences turn genes on...

Genes and Behaviour

Process EnvironmentalRegulatory genes

Environmental influencesturn genes on and off

Structural Genes

Enzyme production

Enzymes

Carbohydrates, fats & proteins

Physical (e.g. temp)

Regulated biochemical reactions

Cell metabolism

Carbohydrates, fats & proteins

Environmental influences (e.g. visual input for the development of the CNS)

Physiological mechanisms

Development of nervous, skeletal & endocrine systems

BEHAVIOUR

Environmental influences(e.g. social environment)Sensory perception, CNS processing,Motor generation

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

In females, neurons die

Expressed in ~1.5% of neuronsBut in all sensory neurons involved in courtship

Effects of fru gene are concentrated in certain sensory neurons

Drosophila Courtship

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.

INHERITANCE OF SONG PATTERNS IN CRICKETS (BENTLEY, 1971)

Teleogryllus commodus Teleogryllus oceanicus

X

F1 hybrid

1. Study of Mendelian Traits

INHERITANCE OF SONG PATTERNS IN CRICKETS

(BENTLEY, 1971)

Teleogryllus commodus Teleogryllus oceanicus

F1 hybrid

X X

T. oceanicusx

F1 backcross

T. commodus X

F1 backcross

1. Study of Mendelian Traits

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

- larger

- hold mating territories

- more colourful

- smaller

- don’t hold mating territories

- less 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 U - no uncapping

r - removal R - no removal

Female (uurr)

X

Male (UR)

Non-hygenic

All females - non-hygenic(UuRr)

Hygenic

Foulbrood in Honeybees

Now do various backcrosses F1 females to males

Genotype No uncapping

Uncapping No removal

Removal

U_R_ * *

u_R_ * *

U_r_ * *

u_r_ * *

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

Model with eyes

Model with no eyes

Frequency of fleeing

2. Inbreeding

Inbred strains of Macropodus opercularis - Miklósi et al (1997)

P strain

S strain

Model with eyes

Frequency of backing

Quantitative Genetics

1 allele 2 alleles

X allelesFor any trait:

Total variance = genetic variance + environmental variance

Or VT = VG + VE

Heritability = VG + VE

VG

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 Microtus ochrogaster

Meadow vole 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

Cross-fostered meadow voles

Controlmeadow voles

Males

Females

Offer more careto 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

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✖

There is a problem in forming a memory

Dunce and rutabaga genes - Drosophila

ATP

Adenylyl cyclase

cAMP cAMP phosphodiesterase

PKA

activates

Binds and activates

Turns on genes that cause changes in structure and function of nerve

cells that govern memory

CREB

Artificial Selection - Drosophila geotaxis

Selection of positively and negativelygeotactic Drosophila • •

• •

•• •• •

•• •

••• •

•• •• •

•• •

•

Negatively geotactic

Positively geotactic

Breed together

Breed together

Artificial Selection - Drosophila geotaxis

Selection of positively and negativelygeotactic Drosophila

Fast maters Control Slow maters

Artificial selection - mating speed in Drosophila

First half of 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

Path length Path length

Sitter Rover Sitter RoverP1

Path length

Sitter Rover

Path length

Sitter Rover

F1 F1x

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

Mid-parent score (P1 + P2)2

••

•

•

••

•••

•

••

• •

•

Slope = heritability

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 Mutated fosB rat

Nursing Retrieving

Hypothesized action of fosB

Odour of rat pups

Odour activatesfosB gene in preoptic hypothalamus

Maternal behaviour

Female rat

FosB mutant Normal

Gene activation in hypothalamus

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

FosB mutantNormal

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 genesOther genesOther genesOther genes

fosB is necessary but not sufficient to induce maternal behaviour

So far – talked about the genetic contribution to a trait

What about the environmental contribution?

Heritability = VG + VE

VG

VG + VE

Dominance Relationships of Cichlid Fish

Astatotilapia burtoni

Territory holders Subordinate males

S. Burmeister

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

Increase in GnRH activity

Increase in GnRH receptors in pituitary gland

Increase in GnRH receptors in pituitary gland

Increase in GnRH production

Size increaseSexual developmentColour change

Dominance Relationships of Cichlid Fish

Subordinate male – grows quickly

Becomes dominant

Social stimuli

Activation of gene for somatostatin

Production of somatostatin

Inhibition of growth hormone

Dominance Relationships of Cichlid Fish

If a dominant male is removed (predation)

Loss of social input

Activation of immediate early gene - erg-I

Triggers changes in GnRH

Changes in colour and aggressive behaviour (minutes)

Changes in fertility (1 week)

Dominance Relationships of Cichlid Fish

If a dominant male is removed (predation)

Loss of social input

Activation of immediate early gene - erg-I

Activity is greatest in areas of brain rich inGnRH-releasing neurons

Erg-I codes for proteins that regulate activity of GnRH

Development of subordinate