Ch.28: Complex and Quantitative Traits

Question 1

What are complex traits?

Answer 1

traits that are determined by multiple genes and influenced by environmental factors

Question 2

What are quantitative traits?

Answer 2

-traits that can be described numerically
-continuous traits: do not fall into
discrete categories (ex. height/weight)
-some are meristic traits: expressed in whole numbers
-threshold traits: inherited due to the contributions of many genes (ex. diseases)

Question 3

Describe variance

Answer 3

the deviance from the mean for measurable values in a group; the statistical value standard deviation (SD) can be derived from the variance value

Question 4

What is Polygenic inheritance?

Answer 4

refers to the transmission of traits that are governed by two or more gene

Question 5

What are polygenic traits or phenotypes are influenced by?

Answer 5

both the genetic makeup and the environment; Environmental impact increasingly skews the
Mendelian inheritance ratio as more and more genes
are involved

Question 6

What is heritability?

Answer 6

the amount of phenotypic variation within a group of individuals that is due solely to genetic variation; Both genetic variance and environmental variance contributes to the overall phenotypic variance that is
observed for a trait

Question 7

What is broad sense heritability?

Answer 7

-takes into account all of the different types of genetic variation
that may affect the phenotype

Question 8

What is narrow sense heritability?

Answer 8

The heritability of a trait due solely to the additive effects of alleles (VA);
The closer the relationship between genetically related individuals the higher the rexp becomes

Question 9

What is selective breeding?

Answer 9

the modification of phenotypes in plant and animal species of economic importance; also called artificial selection

Question 10

What is a consequence of inbreeding?

Answer 10

-the overall reduction in genetic variation within a group
It may promote homozygosity for deleterious alleles, a phenomenon known as inbreeding depression
-Heterosis or hybrid vigor: when two different inbred strains are crossed to each other, the offspring are more vigorous than either parent
-Heterosis can be explained by both the dominance hypothesis or overdominance hypothesis