Exam 21: Genetic Analysis of Quantitative Traits

Of mean,median,and modal,what value is the most common value in a given population?

If H₂ for club foot is estimated as 80%,would you expect a small difference such as 30 versus 27 between MZ and DZ twins,or a large difference,such as 30 versus 2?

If you know the proportion of F₂ individuals that are of parental phenotypes,what formula will tell you how many gene pairs are influencing the trait?

Which of the following is most typical of a case of quantitative inheritance?

A hypothetical condition in some domesticated fowl is identified phenotypically by patchy loss of feathers on the animals' backs.Although several factors,genetic and environmental,are found to be involved,only about 3% of any population with any of these factors are found with feather loss.Which of the following is a likely cause?

For the following traits,the concordance (occurrence of the same phenotype)of MZ and DZ twins are given as percentages.Which trait shows the most genetic as opposed to environmental influence?

If a trait results from genetic variation as well as environmental factors,it is known as a ________ trait.

Although a polygenic trait is influenced by the effect of several genes,one or more of these may be major genes;but many others with lesser effects are known as what type of gene?

Although no specific gene alteration has yet been demonstrated as a cause for schizophrenia (SZ),it is known to have a strong genetic component.A recent study has found a strong association between SZ and a locus at chromosome 10q22-23 in Ashkenazi Jewish and Taiwanese Han populations.Which of the following is probable?

As an H²value approaches 0.0,which of the following must be true?

Distinguish between broad sense heritability and narrow sense heritability,and explain how either or both of these measures can be used to inform those using artificial selection.

If we suppose that a specific QTL is genetically linked to a DNA marker at a recombination frequency of 10%,then the parental type combinations in gametes would be expected at what frequency?

If the odds ratio for a particular QTL/DNA marker pair (e.g.,Q₁₀M₁₀)is 2.2,this indicates that the organism is how many times more likely to get Q₁₀M₁₀ gametes?

What two measures describe the distribution of a trait in a sample?

A group that is experimenting with selection in an insect species due to exposure to a newly developed insecticide,cpd AW143,has found that,after 10 generations of exposure,the population is now bimodal in its response to the drug.Close to 30% of the population are completely normal while 70% live only about 1/6 of the normal lifetime.This is an example of

Sometimes the DNA marker allele and a QTL occur more frequently than would otherwise be expected,either because they interact or because of natural selection.What term describes this?

After the location of a genome region likely to include a QTL,what must be found in this region?

Once a chromosomal position for a putative gene associated with Parkinson disease is verified,which of the following is a next step?

In some traits,different phenotypes result from genes whose alleles each contribute a specific increment to the whole.The phenotypes then have a ________ phenotypic distribution.

Alterations in the ratio of CD4:CD8 lymphocytes are associated with risk of HIV infection progressing to AIDS,of autoimmune diseases,and of progression of some cancers.In searching for predictors of these effects in normal individuals,researchers have found two independent QTLs in the region of the genome known as the major histocompatibility complex (MHC),one in a region regulating CD8 and the other in a region regulating CD4.What does this indicate for the general population?