Animal Behaviour Week 4: Genes and heritability

What are most traits?

most traits are polygenic

• many genes are involved in expression of the trait

Anxiety and Fish

• placed fish from three groups with a predator

• high inspection fish are willing to go close to her predator and did not have adaptive anxiety towards it

• low inspection stays away from the predator because they developed adaptive anxiety, more likely to stay alive 

QTL

region of DNA that is associated with variation in a quantitative trait

QTL for emotionality in rats 

put rats in an arena with no shelter 

• rats had varying levels of nervous shits 

• varying levels of anxiety which means it is polygenic 

• so, the QTL is marked on multiple chromosomes 

Emotions are…

adaptive

ex. we think bisons are cute due to life experience but we should have a lot more anxiety around them because they are deadly whereas we have more anxiety towards spiders that are less deadly

Adaptive emotion experiment in bees

young and old beed, which will become foragers?

• if there are not enough old bees, young bees will prematurely become foragers

• bees have 2000 genes that showed different expression in nurses and foragers

the for gene

• 2000 out of 5500 genes included in DNA microarrays showed different expression in nurse and forager bees 

What are the measures of variation

• variance

• standard deviation

• standard error

Normal distribution

• higher variance means individuals are more different

• symmetric around the mean

• looks like a bell shaped curve

• highest point is the mean

Phenotypic Variance calculation

genetic variance + environmental variance 

• Vp = Vg + Ve 

Broad Sense heritability formula

H^2b = Vg / Vg + Ve

Narrow Sense heritability formula

h²n = Va / Vp

• A = additive genetic variance

• P = phenotypic variance

Indirect fitness

• if another part of the lineage is able to reproduce your genes

Direct fitness

you yourself are reproducing your own genes

Hamilton’s rule 

• used to determine degree of relatedness between individuals 

• rb>c 

• b = benefit to recipient 

• c = cost to the actor 

• r = relatedness to actor