Personality & genetics

Question 1

Are there are any personality traits which show no or little genetic influence? Is there a difference in the heritability of E for males vs. females?

Answer 1

No. No

Question 2

What % of genetic dominance effects do MZ & also DZ twins share? Why?

Answer 2

MZ: 100%. DZ: 25%. Because MZ twins’ genes are identical, whereas DZ twins share 50% of their DNA & so there is only a 25% probability that they share the same 2 alleles of a gene. There is also a 25% P(they share neither allele) & a 50% P(they share one allele)

Question 3

Why do full siblings has a 25% P of sharing dominance genetic effects like DZ twins?

Answer 3

Because the father has 2 alleles for gene A (one from his mother & one from his father) & the mother has 2 alleles for gene A. There are consequently 4 different combinations of mother + father alleles which can arise in the children

Question 4

If genetic dominance effects contribute to trait variance, then the assumption that DZ twins would show 50% of the amount of trait similarity exhibited by MZ twins is flawed because…

Answer 4

DZ twins only in fact share 25% of genetic dominance effects, which will pull the amount of trait similarity down from that predicted by only additive genetic effects

Question 5

Parents/offspring & half siblings share ___% of genetic dominance variation because…

Answer 5

0% because it’s only ever possible for them to share one allele

Question 6

Epistasis effects will be identical for identical twins, where DZ twins are…

Answer 6

Unlikely to share many configurations of interactions between genes at different sites on each chromosome

Question 7

There is especially little influence of the share environment on culture traits i.e.

Answer 7

Openness

Question 8

Define i2, c2s and c2mz

Answer 8

i2 = epistasis effects, c2s = environment shared by siblings, c2mz = environment shared by MZ twins which is likely even more similar than that shared by siblings

Question 9

Sensation seeking is a facet of ___. It also related to conscientiousness and has a heritability of ___%. It was the first normal trait to be…

Answer 9

Extraversion. 60%. Linked to a gene

Question 10

Sensation seeking can be split down into 3 sub-facets, each which show moderate heritability. What are they?

Answer 10

Disinhibition (social risk taking). Thrill seeking (physical risk taking). Boredom susceptibility

Question 11

There is as high a correlation between identical twins reared ___ as between identical twins reared together on non-Big-5 traits. Heritability is about .5 and nonadditive genetic variance appears…

Answer 11

Apart. Unlikely for half of the traits

Question 12

According to the lecture slides the % variance explained by non-shared environmental factors in adoptive siblings is __ for personality, __ for psychopathology & __ for cognitive abilities in childhood vs. __ in adolescence. In contrast, attitudes…

Answer 12

5%, 0%, 25%, 0%. Are affected by the non-shared environment more

Question 13

Give an example of an objective measure of family environment

Answer 13

The filming of mothers’ interactions with children

Question 14

Describe the difference between a linkage and association study

Answer 14

Linkage: after finding that a disease runs in a family you look for genetic markers present across generations. If found, the gene implicated must reside in a given area. Association: is allele X more common in Pp with the disease than those without it?

Question 15

List some characteristic differences between linkage and association study requirements

Answer 15

Linkage vs. association: Requires families vs. doesn’t, does not require matching vs. does, weak vs. powerful, poor vs. high spatial resolution, initial detection vs. fine mapping, rare vs. common alleles