Quantitative Genetics

Question 1

Discrete phenotypes

Answer 1

Clearly defined by 1 or a few genes
No degrees of severity
Only a few traits follow this mode of expression

Question 2

Quantitiative traits

Answer 2

Measurable in numeric terms
Controlled by multiple genes and environmental factors
Have continuous variation

Question 3

Continuous variation

Answer 3

Phenotypes are distributed along a continuum

Series of intermediate phenotypes that fall between 2 extremes

Question 4

Additive alleles

Answer 4

of copies of these alleles influence the degree of severity of the trait

Question 5

Distribution of quantitative traits on a graph

Answer 5

Bell curve: environment blurs phenotypic classes

More phenotypic variance, broader curve

Question 6

Distribution

Answer 6

Summary of continuous phenotypic variance for a group/population

Question 7

Traits that a representative sample has

Answer 7

Randomly selected, large, unbiased (includes all phenotypes)

Question 8

Phenotypic variance (Vp) formula

Answer 8

Vp= Vg + Ve + Vg*e
Vg= genotypic variance
Ve= environmental variance
Vg*e= genotype-by-environment variance

Question 9

Genotypic variance (Vg)

Answer 9

Contribution of allelic differences at multiple genes

Question 10

Environmental variance (Ve)

Answer 10

Contributions from non-genetic sources

Question 11

Heritability

Answer 11

How much of the phenotypic differences are due to genetic factors
Expressed in a number ranging between 0-1 (0- none, 1- all)

Question 12

Phenotypic variance in monozygotic twin studies

Answer 12

All phenotypic variance is due to Ve

Question 13

Quantitative trait loci (QTL)

Answer 13

Loci that influence quantitative traits

Question 14

Genetic architecture of a trait

Answer 14

All QTLs and how they interact