Exam 18: The Genetic and Environmental Basis of Complex Traits

The scatterplots below show the relation between the average phenotype of parents (x-axis) and that of their offspring (y-axis) for three traits. One trait has a heritability of 90% (comparable to that of fingerprint ridge count), another has a heritability of 50% (comparable to that of human height), and yet another has a heritability of 25% (comparable to that of human longevity). To make the axes comparable, for each trait the phenotypic measurement is expressed as a deviation from the overall mean in multiples of the standard deviation. The fact that all of the lines slope upward means that:

If the value of the trait in 16% of the population is equal to 6 or greater, in what percentage of the population is the value of the trait greater than 4?

The plots shown here depict several possible outcomes of an experiment comparing the mean phenotype of a behavioral trait in two strains of mice in three environments. Strain 1 is represented by filled circles and Strain 2 is represented by open circles. Environment 1 (E₁) is deficient in stimulation for the behavior, environment 2 (E₂) has an average level of stimulation, and environment 3 (E₃) is enriched in stimulation. Which of the possible results indicates the absence of genotype-by-environment interaction?

Red coloration in wheat seeds is a complex trait influenced by three unlinked genes, each with two different alleles A and a; B and b; C and c. This Punnett square shows the results of a mating between two plants that are both heterozygous at all three loci. The intensity of the red color phenotype is influenced by only one of the gene products.

When differences in the phenotype due to the environment can be ignored:

In which of the complex traits shown here is variation determined almost completely by heredity?

Which of the traits depicted here illustrates regression toward the mean?

Studies have shown that 5%-10% of all breast cancers are related to mutations in BRCA1 and BRCA2. A logical conclusion from these data is that:

If the concordance rate for a given trait is 10% for both identical and fraternal twins, this means that:

Which of the following are complex traits?

Which of the following traits would you expect to conform to a normal distribution?

Which of the graphs below would likely represent the distribution of a simple, single gene trait?

Salt intake is associated with an increased likelihood of high blood pressure and is therefore a(n) _____ of this common disorder.

Consider a trait determined by a rare, simple Mendelian, autosomal recessive allele. What is the concordance between identical twins? Between same-sex fraternal twins?

Personalized medicine matches the treatment to the disease, not to the patient.

Diets high in fat and carbohydrates affect inbred lines of mice differently. One line becomes obese and the other does not. This is called a _____ interaction.

Lindsay and Joy are twins that share the same genetic material and appear so similar that their teachers cannot tell them apart. Lindsay and Joy are _____ twins.

The scatterplots show the relation between the average phenotype of parents (x-axis) and that of their offspring (y-axis) for two traits in a variety of tropical sweet corn. One trait is ear height, which has a heritability of 75%; and the other is ear length, which has a heritability of 25%. To make the axes comparable, for each trait the phenotypic measurement is expressed as a deviation from the overall mean in multiples of the standard deviation. Which of the following matchups is CORRECT?

Which of the traits depicted here has the SMALLEST heritability?

Personalized medicine matches the treatment to the: