Heredity

Question 1

What is implied in nature vs. nurture?

Answer 1

There is a constant debate to try to determine to what extent behavior is due to genetics vs. environment (ex: dog breeds have a personality).

Question 2

What is Mendel contribution?

Answer 2

He discovered heritability of discrete traits.

Question 3

What was Galton’s work and why?

Answer 3

He studied what traits were heritable and to what extent. He developed statistical methods such as the standard deviation by doing so. He ended up to develop the field of eugenics (improvement of a race through selective breeding) because he feared the human race quality was declining.

Question 4

What is Fisher’s contribution in genetics?

Answer 4

1. Invented ANOVA

2. Reconciliation of discrete traits and continuous traits inheritance.

Question 5

What is Goddard’s contribution in eugenics?

Answer 5

Invented the IQ test which revolutionized the way immigrants and soldier in the army were selected (some person even got sterilized), but the test was kind of biased.

Question 6

What was J.B. Watson contribution in eugenics?

Answer 6

For him, you could be trained to have a certain behavior and it had nothing to do with genetics (ex: little Albert experiment)

Question 7

Can behavior be selected in mammals?

Answer 7

Yes indeed. By example, if you select rats to breed according to the time spent running on a wheel, you can get a statistically significant difference in time spent after 12 generations (Rundquist).

Question 8

Give an example of an experiment that helped to prove that gene effects can be additive.

Answer 8

Looked at how fast Drosophila with red, brown or white eyes got to a light.
Red = 17,9s
Brown eyes with a red background were slower than pure brown eyed flies.
White eyes with a red background were WAYYYYY slower (32s) than those without a background and brown eyed flies as well. It showed that the gene coding for white eye had an effect while red too and those effects were additive.

Question 9

What was the geotaxis experiment?

Answer 9

Selected in what direction flies were going and saw that they could show negative or positive geotaxis depending on how the flies were selected, so the behavior was heritable. Then, they looked at what effect you get on taxis when you select for certain sets of chr.. They saw the genes were distributed across all chormosomes (genes on 2 chr. respond to positive selection while genes on 1 chr. respond to neg. selection.

Question 10

How can heritability be measured?

Answer 10

Var(P) = Var(G)+ Var(E) + 2Cov(G,E) 
Setting Cov(G,E) = 0  (i.e. a particular genotype is not more  likely to be found in particular environment)
h2 = Var(G)/Var(P) = Broad sense heritability = (Var(P) – Var(E))/Var(P) 
VAr(P) = variance accross unselected population, Var(G) in selected strains = 0

Question 11

How can we get Var(G) in a human population?

Answer 11

We use twin studies with monozigotic twins (no difference between genes, only environment) vs. dizigotic tiwns (difference between genes and environment).