Heritability

Question 1

Discrete Traits (Definition and list two examples)

Answer 1

Traits in which only one or a couple of genes determine the trait. An example is eye color and pea plant texture (wrinkled or smooth). Usually have two alleles determining trait within the gene.

Question 2

Continuous Traits

Answer 2

Traits determined by numerous genes (and thus numerous alleles). Example include height, hair color, obesity

Question 3

What two components make up the phenotype of an individual?

Answer 3

Genes and enviroment

Question 4

Polygenic Traits

Answer 4

Traits determined by more than one gene (usually continuous)

Question 5

What causes continuous variation?

Answer 5

The combination of the effects of genes and environment

Question 6

In which case is it easier to predict genotype from phenotype in terms of genes and the environment?

Answer 6

Easiest to predict when environment is having very little effect on expression of the genes

Question 7

Vp

Answer 7

Total phenotype variation

Question 8

Vg

Answer 8

Variation from differences in genetic factors

Question 9

Ve

Answer 9

Variation from environment

Question 10

VgXe

Answer 10

Variation due to the interaction between genes and environment

Question 11

Heritability Equations

Answer 11

Vp=Vg+Ve+Vgxe

h^2=Vg/Vp

Question 12

Heritability in own words:

Answer 12

The genetic variation in a population accounted for by genes

Question 13

What tests is used to discover heritability?

Answer 13

An ANOVA to compare differences in variation and regression to compare parents to offspring

Question 14

How are regression lines used in twin studies?

Answer 14

To compare a trait in one twin to a trait in the other twin and analyze the slope

Question 15

What does rMZA represent?

Answer 15

The correlation coefficient of a certain trait among monozygotic twins

Question 16

Correlation equation for rMZA?

Answer 16

=Vg+Ves/ Vt

Question 17

What is special about Ves in the correlation equation?

Answer 17

It is negligible because the twins are said to be reared in different locations with different enviroments

Question 18

What does the Ves negligible assumption lead to?

Answer 18

Overestimate in heritability because although twins weren’t reared together, they may have shared similar enviroments

Question 19

4 Criticisms of Twin Studies

Answer 19

1) Ignored shared environment in identical twins or unshared environment in twins raised together
2) Mono-zygotic twins not genetically identical
3) Twins are NOT a random sample of population
4) Twins could seek out same niche based on SMALL number of genetic similarities

Question 20

What is the misassumption regarding what heritability measures?

Answer 20

Not a measure of genetic control within an individual, but the extent to which genetic differences among individuals within the population influence the trait

Question 21

Genome Wide Association Study

Answer 21

Measures the association between SNP’s in population and phenotype and looks at the function of genes associated with those SNPS determining phenotype

Question 22

What is the reason for missing heritability in the GWAS?

Answer 22

We do not have the entire genome for each patient so some of the variation is not captured in the SNP’s

Question 23

What kind of SNP’s will you have if you have a common disease with a common variant?

Answer 23

Many small effect SNP’s