Exam 22: Quantitative Genetics

In parent-offspring regression,the average value of the parents is termed the

A ________ trait is typically influenced by one or two genes.

The proportion of phenotypic variance that results from additive genetic variance is known as ________ heritability.

A broad-sense heritability of 0.8 for a particular trait indicates that

In Mendel's day,"particulate" inheritance would have made less sense to people than blending inheritance.Why?

Distinguish between polygenic and multifactorial traits.

Explain why narrow-sense heritability is a more accurate indicator of responsiveness to selection than is broad-sense heritability.

Ornamental hydrangeas are well known to produce either blue or magenta flowers,depending on soil pH.This may be a good example of a discrete trait influenced by

A quantitative trait influenced by four loci,each with two alleles,would be expected to show ________ possible genotypes.

When graphing a distribution of phenotypes for a continuous trait,a broad curve implies

Populations of the snail Cepaea nemoralis exhibit three color morphs,a good example of a ________ trait.

The correlation coefficient is a measure of the strength of association between two traits.Correlation,however,does not indicate causation.Think of one or two variables (not necessarily phenotypes)that are correlated and are causally linked,and one or two variables that may be correlated but are not likely to be causally linked.

An isolated population of wild turkeys has adult males that weigh an average of 18 pounds and females that weigh an average of 10 pounds.Another isolated population living 100 miles north has a population where adult males weigh 13 pounds and females 8 pounds on average.Both populations have a very low phenotypic variance.How could you determine genetic contributions to the weight differences between the populations?

Define,in your own words,the biological meaning of heritability.

Quantitative traits typically have multiple genetic influences in which alleles of a number of genes contribute individual amounts to the final phenotype without classical dominance or epistasis.The term used for the observed variation that results from this is

In descriptive statistics,the median is defined as the value exactly in the center of a distribution,with half the values lying above and half lying below.

The broad-sense heritability of a trait is estimated at 0.8.If the total phenotypic variance is estimated at 32.20,what is the genetic variance?

Identical (monozygotic)and fraternal (dizygotic)twins provide a natural experiment for investigating the influence of genetics on traits.Outline a study approach using twins,assuming you could identify enough pairs,in which you are examining the relative contribution of genetics on blood cholesterol level.

A botanist studying a plant with geographically separated and morphologically distinct populations wants to know the degree to which the differences between the populations are attributable to genetic factors.Outline a simple experiment she can perform to address this question.

A female cat that is small due to nutritional deficiencies experienced in early life will give birth to smaller kittens than a genetically identical cat that is larger in size due to better nutrition in early life,even if both female cats were bred to the same male cat and both had good nutrition during pregnancy.The term that is used in measuring this type of variation is