3. Extensions to Mendelian Inheritance
Overview of interacting Genes
- Open QuestionThree pairs of genes with two alleles each (A₁ and A₂,B₁ and B₂, and C₁ and C₂) control the height of a plant. The alleles of these genes have an additive relationship: Each copy of alleles A₁,B₁, and C₁ contributes 6 cm to plant height, and each copy of alleles A₂,B₂, and C₂ contributes 3 cm.What height is expected in the F₁ progeny of a cross between A₁A₁B₁B₁C₁C₁ and A₂A₂B₂B₂C₂C₂.
- Multiple Choice
Which of the following terms describes an interaction between two genes?
- Multiple Choice
Polygenic traits are controlled through which of the following ways.
- Multiple Choice
Polygenic traits are usually continuous traits?
- Open Question
Which of the following traits would you expect to be inherited as quantitative traits?
coat color in dogs - Open Question
For the traits listed in the previous problem, which do you think are likely to be multifactorial traits, with phenotypes that are influenced by genes and environment? Identify two environmental factors that might play a role in phenotypic variation of the traits you identified.
- Open QuestionWrite a short essay that explains why multiple and lethal alleles often result in a modification of the classic Mendelian monohybrid and dihybrid ratios.
- Open Question
Compare and contrast broad sense heritability and narrow sense heritability, giving an example of each measurement and identifying how the measurement is used.
- Open Question
In a cross of two pure-breeding lines of tomatoes producing different fruit sizes, the variance in grams (g) of fruit weight in the F₁ is 2.25 g and the variance among the F₂ is 5.40 g. Determine the genetic and environmental variance (VG and VE) for the trait and the broad sense heritability of the trait.
- Open Question
Describe the difference between continuous phenotypic variation and discontinuous variation. Explain how polygenic inheritance could be the basis of a trait showing continuous phenotypic variation. Explain how polygenic inheritance can be the basis of a threshold trait.
- Open Question
Calculate the mean, variance, and standard deviation for a sample of turkeys weighed at 8 weeks of age that have the following weights in ounces: 161, 172, 155, 173, 149, 177, 156, 174, 158, 162, 171, 181.
- Open Question
Provide a definition and an example for each of the following terms:
threshold trait