Lecture 14: Behavioural Genetics

Question 1

***How can heritability estimates be calculated from twin studies?

Answer 1

1. Monozygotic twins raised together
2. Dizygotic twins raised together
3. monozygotic twins raised apart
4. adopted siblings

Ratio of Phenotype variance/Genetic variance

Question 2

***What is a quantitative genetic analysis of

behaviour?

Answer 2

1. characterize quantitatively a behavioural phenotype in a given population/strain derived from nature or by artificial selection
2. Examining the changes in phenotype in sets of progeny from test crosses between different populations
3. infer statistically the number of genes responsible and their interactions

Question 3

***What are single gene studies of behaviour?

Answer 3

Testing hypothesised genes from quantitative analysis.

=> Studying the contribution of likely candidates for a phenotype based on what is known about their neurobiological bases
– Alcohol dehydrogenase for alcoholism

Question 4

***What are the problems in explaining behaviour with genetics?

Answer 4

1. lack of evidence for any complex psychological trait that is determined by a single gene
2. meaning of genetic marker
   vagueness in incorporating a mechanistic role for the gene in the phenotype
3. a definitional problem with behaviour

Question 5

The measurable expression of a trait is the

Answer 5

phentotype

Question 6

what is the Phenotypic variance formula?

Answer 6

(Vp) = Vg + Ve + Vge

note:
Vg = Genetic variance
Ve = Environmental variance
Vge = Gene-Environment interac4ons

Question 7

_____________ is the component of the variance
of the phenotype that can be explained by
heritable factors

Answer 7

heritability

Question 8

what is the formula of heritability quotient of a trait?

Answer 8

h2 = V(g) / V(p)

Question 9

problems with quantitative analysis

Answer 9

1. Results do not identify individual genes
2. Necessity for large pedigrees & crossmating
   makes human studies unlikely

Question 10

problems with single gene analysis

Answer 10

1. Ignores the important contribution of
   background genotype to phenotype
2. Redundancy and pleiotropy in mechanisms
3. Ignores roles for adapta4on and
   developmental effects