Lecture 1

Question 1

ADE model: whats the MZ correlation between the D’s between the two twins?

what is the DZ correlation?

Answer 1

ADE model:

MZ correlation: 1

DZ correlation: 0.25

Question 2

what is one of the problems with finding a gene for intelligence?

Answer 2

there is a long distance between the output of a gene and the score on an IQ test

Question 3

Biometrical Genetic model:

what are genotypic values?

Answer 3

genotypic values:

-a / d / a

> if dominance is absent, then d = m

Question 4

polygenetic effects: how many genotypes/phenotypes with

1 gene

2 genes

3 genes

what happens when many genes are involved?

Answer 4

1 gene: 3 genotypes, 3 phenotypes

2 genes: 9 genotypes, 5 phenotypes

3 genes: 27 genotypes, 7 phenotypes

many genes: distribution of genotypic values is normally distributed

Question 5

how to interpret heritability?

Answer 5

interpretation heritability

1. applies to population
2. highly heritable does not mean incurable
3. changes in heritability can be caused by changes in genes and changes in environment
4. heritability within population cannot be generalized to other populations
5. heritability cannot explain differences between populations

Question 6

how do we get from twin data to a testable mathematical model?

Answer 6

through path analysis

Question 7

what are 3 assumptions of the twin design?

Answer 7

1. no GxE interaction
2. no G, E correlation
3. no assortative mating

Question 8

what are the advantages and limitations of the twin design?

Answer 8

advantages: you don’t have to genotype or measure environment
limitations: 1. cannot test which gene or what environmental factor has effect
2. based on many assumptions

Question 9

example of GxE interaction: SES and IQ

Answer 9

Low SES: strong C influences, low A influences on IQ

High SES: low C influences, strong A influences on IQ