Exam 21: Quantitative Genetics and Multifactorial Traits

What is the name of the process of selecting a specific group of organisms from an initially heterogeneous population for future breeding purposes?

Name the three components of phenotypic variance.

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

In the early part of the twentieth century, Nilsson -Ehle and others described experiments showing that multiple loci may be involved in the inheritance of certain traits. Such patterns are often called _.

Assume that in the F2 of a series of crosses, 1/64 of the offspring resemble one of the parents (P). How many gene pairs are involved in producing these results?

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

Environmental factors typically influence inheritance of

Traits such as height, general body structure, skin color, and some behavioral traits are probably caused primarily by genes that behave codominantly or epistatically.

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

Some traits are polygenic but do not show typical continuous distributions. For example, type II diabetes is determined by a number of genes, but one is either diagnosed as diabetic or not diabetic based on blood sugar levels. How might one explain such a phenomenon?

How many gene pairs are involved in generating a typical 1:4:6:4:1 ratio?

What are the name and formula for describing sample variability?

Quantitative inheritance involves the interaction of a number of gene loci. The pattern of Genetic transmission typical of quantitative inheritance is

Provide a formal equation for h2 (narrow -sense heritability).

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

If the proportion of F2 individuals resembling either of the two most extreme parental phenotypes can be determined, which formula can be applied to determine the number of gene pairs involved?

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.

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

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

Assume that four polygenic gene pairs are involved in determining phenotypes of F2. How many phenotypic classes are expected?