genes and behaviour. process environmental regulatory genes environmental influences turn genes on...
TRANSCRIPT
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Genes and Behaviour
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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
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Drosophila Courtship
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Drosophila Courtship
fru gene – one in a hierarchy
Gene A affects
Gene B affects
Gene C
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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
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Effects of fru gene are concentrated in certain sensory neurons
Drosophila Courtship
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Mutants of fru gene
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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
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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.
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INHERITANCE OF SONG PATTERNS IN CRICKETS (BENTLEY, 1971)
Teleogryllus commodus Teleogryllus oceanicus
X
F1 hybrid
1. Study of Mendelian Traits
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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
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1. Study of Mendelian Traits
Ruffs - Philomachus pugnax - (Lank et al, 1995)
MALES - 2 KINDS
Satellite Independent
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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
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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
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Foulbrood in Honeybees
Under the control of two alleles
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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
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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_ * *
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2. Inbreeding
Inbred strains of Macropodus opercularis - Miklósi et al (1997)
Two strains - S and P
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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
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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
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2. Inbreeding
Inbred strains of Macropodus opercularis - Miklósi et al (1997)
P strain
S strain
Model with eyes
Frequency of backing
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Quantitative Genetics
1 allele 2 alleles
X allelesFor any trait:
Total variance = genetic variance + environmental variance
Or VT = VG + VE
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Heritability = VG + VE
VG
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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
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2. Inbreeding to show the role of the environment
-to detect postpartum maternal influences
CROSS-FOSTERING
Microtus pennsylvanicus Microtus ochrogaster
Meadow vole Prairie vole
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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)
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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
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Twin Studies
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Inducing mutations
Normal Drosophila- can learn to associate shock and odour
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Inducing mutations
Mutant Drosophila- dunce gene can’t learn to associate shock and odour
- On X-chromosome
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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
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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
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Artificial Selection - Drosophila geotaxis
Selection of positively and negativelygeotactic Drosophila • •
• •
•• •• •
•• •
••• •
•• •• •
•• •
•
Negatively geotactic
Positively geotactic
Breed together
Breed together
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Artificial Selection - Drosophila geotaxis
Selection of positively and negativelygeotactic Drosophila
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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
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Artificial Selection – Mus musculus nests (Lynch, 1980)
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Hybridization experiments - Sokolowski
Path length Path length
Sitter Rover Sitter RoverP1
Path length
Sitter Rover
Path length
Sitter Rover
F1 F1x
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Hybridization
Alleles are forS and forR
Rovers are forRforR or forRforS
Sitters are forSforS
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Hybridization Experiments - Lovebirds
Peach-faced Fischer’s
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Parent Offspring Regression
Activity scores with Drosophila
Offspring
Mid-parent score (P1 + P2)2
••
•
•
••
•••
•
••
• •
•
Slope = heritability
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F. Comparative approach - Temperature selection in Peromyscus
Preferred Temperature (Adults)
-5
0
5
10
15
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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
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fosB gene in rats
Normal rat Mutated fosB rat
Nursing Retrieving
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Hypothesized action of fosB
Odour of rat pups
Odour activatesfosB gene in preoptic hypothalamus
Maternal behaviour
Female rat
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FosB mutant Normal
Gene activation in hypothalamus
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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
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Mammary Development in Rats
FosB mutantNormal
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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
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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
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So far – talked about the genetic contribution to a trait
What about the environmental contribution?
Heritability = VG + VE
VG
VG + VE
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Dominance Relationships of Cichlid Fish
Astatotilapia burtoni
Territory holders Subordinate males
S. Burmeister
Burmeister et al 2005. PloS Bio. 3:363
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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
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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
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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
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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)
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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