Exam 23: 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?

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

When a trait is polygenic,but distinguished from continuous and meristic traits by having a small number of discrete classes,it is said to be a(n)________ trait.

To estimate how much the means of a variety of like samples drawn from the same population might vary,what statistic is often used and what is the formula for it?

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

Individuals with the same genetic background and a high degree of homozygosity are said to be isogenic.Of what value are isogenic strains in genetic studies?

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?

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

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?

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.

What is the relationship between the narrow-sense heritability (h²)index and the impact of selection?

Given the following numbers,calculate the mean: 10,12,14,16,18.

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

Typically,one thinks of identical (MZ)twins being genetically identical.However,genomic differences do exist between MZ twins by epigenetic processes.What are epigenetic processes?

Assume that a cross is made between tall and dwarf tobacco plants.The F₁ generation showed intermediate height,while the F₂ generation showed a distribution of height ranging from tall to dwarf,like the original parents,and many heights between the extremes.These data are consistent with which one of the following modes of inheritance?

Assume that you are studying a trait determined by a number of polygenes.If there are seven phenotypic categories,how many genes are probably involved?

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

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

Environmental factors typically influence inheritance of ________.