Exam 21: Quantitative Genetics and Multifactorial Traits

Inbred strains with individuals of a relatively homogeneous or constant genetic background are often used to determine the influence of genes or the environment on phenotypic variation.Variation observed between different inbred strains reared in a constant or homogeneous environment would likely be caused by genetic factors.What would be the source of variation observed among members of the same inbred strain reared under varying environmental conditions?

Characteristics exhibited by continuously varying traits include ________.

Huntington disease is inherited in humans as an autosomal dominant gene.Affected individuals show progressive brain deterioration from cell death in the cerebral cortex.Onset of the disease usually occurs between ages 30 and 50.Give two possible reasons for the observed variation in the age of onset of this disease.

A "marker" in a genetic sense usually represents a site along a chromosome where a specific nucleotide sequence exists.Which specific phrase is used when such markers are identified by restriction endonucleases and a particular set of DNA fragments is generated?

Which two relatively recent extensions to QTL mapping center on molecular definitions of phenotypes with quantitative traits?

Interpret the meaning of an H² (broad-sense heritability)value that approaches 1.0.

Provide a brief definition of the terms additive variance,dominance variance,and interactive variance.

How would the use of a large series of monozygotic and dizygotic twins enhance studies on the genetic basis of human behavior?

List at least three statistical values often used to represent a sample.

Name two human traits that would be expected to have high concordance.

The 9:3:3:1 ratio is typical of a dihybrid cross in which complete dominance and independent assortment occur.What is the dihybrid ratio with independent assortment of polygenes?

Define the term broad-sense heritability (H²).What is implied by a relatively high value of H²? Express aspects of broad-sense heritability in equation form.

Provide a brief description of discontinuous inheritance and continuous inheritance.How are the two related? How are they different?

In the analysis of quantitative traits,positions on chromosomes called quantitative trait loci (QTLs)are often discussed.In the same context,restriction fragment length polymorphisms (RFLPs)are also discussed.What is the relationship between QTLs and RFLPs?

What is the formal expression used to examine the relative importance of genetic versus environmental factors?

Concordance refers to the frequency with which members of a twin pair express a different trait.

Name two mammalian traits with relatively high heritability (h²)values and two with relatively low h² values.

Continuous inheritance is often related to the term quantitative inheritance.Why?

Polygenes are involved in determining continuously varying or multiple-factor traits.

List at least two statistical terms commonly used in the analysis of quantitative traits.