Exam 23: Quantitative Genetics and Multifactorial Traits

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?

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

Characteristics exhibited by continuously varying traits include ________.

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

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

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

What is meant by the term heritability? Describe the components of heritability and provide a brief explanation of each. Of what interest is heritability to animal and plant breeders?

We often refer to the host of genetic factors in the genome that have an influence on a particular gene's expression as its genetic background. What influence does genetic background have over the phenotype of the organism?

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

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?

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

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?

Name the three components of phenotypic variance.

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?

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

Describe the value of using twins in the study of questions relating to the relative impact of heredity versus environment.

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

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

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

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