behavioral genetics 2
TRANSCRIPT
Behavioral Genetics 2 Summer 2016 Positions Available: Benson-Amram Zebra Finch Lab Goal: To investigate personality and problem-solving ability in individual and pairs of captive
zebra finches in Dr. Sarah Benson-Amram’s Animal Behavior & Cognition Lab.
Responsibilities:
x Assist with planning and carrying out behavioral experiments with zebra finches. x Help maintain routine husbandry. x Extract data from video-recorded experimental trials.
Qualities Required of Applicants:
x Interest in animal behavior and cognition x Dedication to the project. x Ability to work odd hours and be flexible with scheduling (this is not a typical 9-5 job!). x Ability to work well with others and independently. x Ability to maintain a positive attitude. x Organization skills and proficiency in use of Microsoft Office.
Benefits:
x Students can earn 1-2 credits for completion of summer work. x Successful volunteers will be encouraged to apply for an EPSCoR grant in the fall to
continue working with the Benson-Amram lab. x Successful volunteers can use this experience on their CV/resume and request letters of
recommendation in the future. x Hands-on research experience.
To be considered for this position, interested candidates must submit the following to
Lisa Barrett ([email protected]) no later than* March 11th:
1) Cover letter or letter of interest 2) CV or Resume 3) 3 references (name and contact information)
*If you are ready to begin this position before Summer 2016, please let us know and we will get you started!
Experimental manipulation of gene function: knockout studies
• Knockout technique – Procedure that eliminates the expression of a gene
• single gene-effects
• insert a non-functional gene sequence, compare the resulting phenotype to the ‘wild-type’
fosB +
fosB -
Social environment and gene expression in birds
• Research question: What is the role of the FoxP2 gene in song development? (Haesler et al. 2007)
• Song system – Area of avian brain that
controls song production
Social environment and gene expression in birds
• Methods: – Zebra finches (Taeniopygia guttata) – Knockdown technique – used a virus to
insert short sections of RNA into FoxP2 gene to reduce its expression
– Controls had short sections of RNA placed in a noncoding region of DNA
– Adult male tutors and young juvenile males housed together
– Recorded songs
Social environment and gene expression in birds
Spectrogram: Allows researchers to characterize acoustic structure of vocalizations
Social environment and gene expression in birds
• Results: – Knockdown birds
had much lower FoxP2 expression than controls
Social environment and gene expression in birds
• Results: – Knockdown birds
tended to omit specific syllables in their songs
• Conclusion: – FoxP2 is required for
normal song development
Microarray Analysis
QTL mapping to identify genes associated with behavior
• Quantitative trait loci (QTL) – Stretches of DNA that either contain or are linked to genes
influencing a trait such as behavior • QTL mapping
– Statistical technique that combines genetic information with trait information to determine which regions of the genome contain the genes that influence the trait QTLs
• Candidate genes – Major genes suspected of contributing to a large amount of
the phenotypic variation in a specific trait
QTL mapping
• Use marker loci that are easily assayed, but causally unrelated to the trait in question to identify the approximate locations of the unknown alleles that affect the behavioral trait of interest
QTL mapping• Step 1: Select two parental strains that a) differ
considerably in their values of the trait of interest and b) differ at a set of marker alleles
Genes and Environment• Have focused on genetic influences on behavior. • However, variation in behavior among individuals
results from both variation in gene alleles and variation in environments.
• How can we characterize the effects of each? • We can quantify the relative contributions of
genetic and environmental variation to behavioral variation by thinking about heritability
Heritability (H2)• Indicates what proportion of the total variance in a trait is
due to variation in genes • Heritability can vary from 0.0-1.0 • H2=0: Phenotypic variation not due to genotypic variation • H2=1: All phenotypic variation due to genotypic variation
– H2 is a relative measure, so depends on the population under investigation
– If H2 is high, can be impetus for investigations to identify the responsible gene(s) &/or the mechanisms of trait expression
(Serrano & Tella 2007)
Heritability of colony size preference in the Lesser Kestrel
One way to determine heritability is to regress offspring phenotype with parental phenotype.
The slope of the regression line approximates heritability of trait (if avg. trait value of parents used).
H2 = 0.53
– Proportion of phenotypic variation in a population due to genetic variation
P
G
VVh =2
• a measure of how strongly a behavioral phenotype is influenced by genetic differences between individuals
Heritability (H2)Total genotypic variation: VG = VA + VD + VI
where
VA = Additive effects, or the average effect of individual alleles on the phenotype VD = Dominance effects, or the interaction between alleles at one locus VI = Epistasis, or the interaction between genes at different loci
Heritability (H2)
Total phenotypic variation: VP=VG+VE+VI
where:
VP= total phenotypic variation observed in a (behavioral) trait
VG= variation in population due to genotype
VE =variation in population due to environment
VI = variation in population due to interaction of VG with VE
Heritability (H2) Heritability (H2)
H2=VG/(VG+VE+VI)
where:
H2= heritability
VG= variation in population due to genotype
VE =variation in population due to environment
VI = variation in population due to interaction of VG with VE
• Gene-environment interaction (GEI) – When environment has greater effect on one
genotype than other
Rover and sitter foraging behavior in fruit flies
• Research question: Do different behavioral polymorphisms in fruit flies exhibit gene-environment interactions? (Kent et al. 2009)
Rover and sitter foraging behavior in fruit flies Rover and sitter foraging behavior in fruit flies
• Methods: – Exposed adult rover and
sitter phenotypes to different levels of food availability (fed or food deprived)
– Recorded movement from food patch
– Used mass spectroscopy to determine compounds stored in head
Rover and sitter foraging behavior in fruit flies
• Results: – Fed rovers had much
higher food-leaving scores than did food-deprived rovers
– No difference between fed and food-deprived sitters
Figure4.16.Adultroverandsitterfood-leavingbehavior.Mean(+SE)food-leavingscoreforfedandfood-deprivedflies.Notethedifferenceinthechangeinsitter(blue)androver(orange)food-leavingscoresbetweenfedandfood-deprivedflies(Source:Kentetal.2009).
Rover and sitter foraging behavior in fruit flies
• Results: – Rovers and sitters store
food differently • Conclusion:
– Gene-environment interactions affect both behavioral and metabolic traits
Development of Behavior Precocial young
Altricial young
The changes in behavior and its underlying mechanisms in individuals from conception to death.
Behavioral Development
The ontogenetic trajectory of a worker honey bee
This includes the behavior of individuals before they are born!
Waddington’s Epigenetic Landscape (1957) as a metaphor for development
Canalization:a particular developmental process may follow a fairly fixed path, resulting in similarity between individuals of the same species.
When a ball moves to the left or right, the slope brings it back on course. Similarly, regulatory mechanisms keep development on track.
Certain internal and external events can trigger development to change course. Different valleys represent the alternative phenotypic traits.
Differentiation
Genetic, physiological and ecological factors are crucial for an individual’s life-history.
Y chromosome
Royal jelly
Humans pass the same developmental milestones as they grow up.
- walk by 18 months - talk by 2 years of age
- reach sexual maturity before the late teen years
These features would be described by Waddington as ‘canalised’.
Spider’s web spinning
Rodent grooming
Some behavior patterns appear stable in a wide range of environments.
Infant smiling
But these behavioral features can still be modified by experience.
6
Blind babies start to smile at the same age as sighted babies.
But sighted people learn to modify their smiles according to their experience.
Blind people are less responsive and less expressive in facial expression, since they lack visual interaction.
Early social environment can affect behavioral development
– Eg., hatching synchrony (23-24 days) in bobwhite quail chicks can be facilitated by chick clicks
• clicks of more developed chicks hastened hatching date of less developed chicks
• clicks of less advanced chicks deferred hatching date of more developed chicks
Early social environment can affect behavioral development
– Female house mouse maturation & puberty ~35 days – if exposed to male urine or estrus female - earlier– if exposed to urine of group-caged females - later
Social development
What social problems confront an organism during its development?
1)Discriminating animate from inanimate objects 2)Identification & classification of prospective
social partners 3)Attainment of skills necessary for competition
& cooperation, establishing a social position Dispersers in social species must do this
twice! 4)Acquire skills associated with mating:
Identifying, finding, selecting, courting, and copulating
5)Develop parenting skills
early social environment can affect behavioral development
Harlow Experiments–Total Isolates:
–non-normal behavior as juveniles–As adults- inappropriate social, sexual and parenting
–Surrogate mothers: –More normal self-directed behavior–Non-normal social and parenting
–Peer groups: –More normal behavior than when reared with mom alone
Social deprivation: rhesus macaque studies
– required only 20 minutes/day of social contact!– Rehabilitation: 6 month old isolate w/3 month
old non-isolate
Ballen et al. 2014
Early social environment can affect behavioral development
– John Bowlby’s work on Attachment in Orphans from WWII
• often unable later to form any lasting, intense ‘love’ relationships
• Critical importance of the young child’s relationship to at least one specific & dependable adult caregiver responsive to child’s emotional and physical needs
• long-lasting emotional bonds that infants develop towards their primary caregiver
Imprinting• Experience in early life
affects later social and sexual preferences
Filial Imprinting
the process by which animals develop a social
attachment to a particular object
Filial imprinting•After hatching, chicks of many species approach & follow conspicuous objects to which they are exposed for a certain amount of time.
•Chicks will even form a social preference for inanimate objects.
•Chicks become distressed when the familiar object is removed.
Critical (“sensitive”) Periodfor Filial Imprinting
mallard ducklings
sensitive period *
* critical period
Colin Gregory