20. Quantitative Genetics

Which of the following represent trait variation caused from genetic variation?

If you wanted to identify what proportion of trait variation is due to the environment, you would do what?

If you wanted to identify what proportion of trait variation is due to genetics, you would do what?

How do we assess environmental factors to determine if they impact the phenotype of a quantitatively inherited trait?

A dark-red strain and a white strain of wheat are crossed and produce an intermediate, medium-red F₁. When the F₁ plants are interbred, an F₂ generation is produced in a ratio of 1 dark-red: 4 medium-dark-red: 6 medium-red: 4 light-red: 1 white. Further crosses reveal that the dark-red and white F₂ plants are true breeding

Predict the outcome of the F₁ and F₂ generations in a cross between a true-breeding medium-red plant and a white plant.

A dark-red strain and a white strain of wheat are crossed and produce an intermediate, medium-red F₁. When the F₁ plants are interbred, an F₂ generation is produced in a ratio of 1 dark-red: 4 medium-dark-red: 6 medium-red: 4 light-red: 1 white. Further crosses reveal that the dark-red and white F₂ plants are true breeding

Assign symbols to these alleles, and list possible genotypes that give rise to the medium-red and light-red phenotypes.

Height in humans depends on the additive action of genes. Assume that this trait is controlled by the four loci R, S, T, and U and that environmental effects are negligible. Instead of additive versus nonadditive alleles, assume that additive and partially additive alleles exist. Additive alleles contribute two units, and partially additive alleles contribute one unit to height.

If an individual with the minimum height specified by these genes marries an individual of intermediate or moderate height, will any of their children be taller than the tall parent? Why or why not?