Exam 23: Quantitative Genetics and Multifactorial Traits

The multiple factor hypothesis suggests that many factors or genes contribute to the phenotype in a cumulative or quantitative manner.

Characteristics exhibited by continuously varying traits include ________.

If one is attempting to determine the influence of genes or the environment on phenotypic variation,inbred strains with individuals of a relatively homogeneous or constant genetic background are often used.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 various environmental conditions?

Interpret the meaning of an H² (broad-sense heritability)value that approaches 0.0.

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

What is the term given to a random subset of individuals who are selected for measurement in a particular study?

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

What formula can be used to determine the number of categories (phenotypes)possible in the F₂ results of a polygenic system?

As used in twin studies in mammals,distinguish between the terms concordant and discordant.

What are the name and formula for describing sample variability?

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

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

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 ________.

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

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

Additive alleles are those that are epistatic over nonallelic genes that influence the same phenotypic characteristic.

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

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

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

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