How can we ascertain the number of polygenes involved in the inheritance of a quantitative trait?

What findings led geneticists to postulate the multiple-factor hypothesis that invoked the idea of additive alleles to explain inheritance patterns?

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

How do we know that monozygotic twins are not identical genotypically as adults?

Write a short essay that discusses the difference between the more traditional Mendelian and neo-Mendelian modes of inheritance (qualitative inheritance) and quantitative inheritance.

Define the following:

(a) Polygenic

(b) Additive alleles

(c) Correlation

(d) Monozygotic and dizygotic twins

(e) Heritability

(f) QTL

(g) Continuous variation

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

Based on the ratios in the F₂ population, how many genes are involved in the production of color?