In this chapter, we focused on a mode of inheritance referred to as quantitative genetics, as well as many of the statistical parameters utilized to study quantitative traits. Along the way, we found opportunities to consider the methods and reasoning by which geneticists acquired much of their understanding of quantitative genetics. From the explanations given in the chapter, what answers would you propose to the following fundamental questions:

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

Video transcript

Welcome back. Let's look at our next question which of the following statements about additive alleles is true. Let's recall what additive values are. And that's when you have multiple genes contributing to a single phenotype. So something like human eye color or human height, human skin color, all those things you have multiple different genes that add together. That's the word additive to create a single phenotype, the height of a person, their eye color. So we have multiple genes contributing to a single genotype. Each of those genes with its own alleles. So let's look through our answer choices noting that choice D. Is both B. And C. So we have choice A. Is dominance or episode. Asus are examples of additive genetic effects. Well this is incorrect dominance and episode Asus involve different alleles but not different genes. So with dominance, alleles are the same locus. So one a little masking the effect of the other and epic stasis. You also have this effect of different alleles and but the alleles are a different Los I so won a little on the distant los I can can mask the effect of an ally in a different place but it's not multiple genes. It's a single gene with multiple alleles whether in the same place or different places. So choice is incorrect choice. B says additive genetic effects occur when two or more genes make a single combined contribution to the final phenotype. And this is exactly what happens with attitude gene effects the choice B is correct. We won't pick that as our answer just yet. Since we do have that possibility of both B and C. Being correct. And then finally, choice, He says, a trait without additive variance lacks very genetic variation. Well, this is incorrect. Um You don't need additive effects to create genetic variation. Even if you have just a single gene, you have mutation, you have recombination, you have selection. All these things introduced genetic variation, even if there's just a single gene controlling the phenotype. So since choice C. Is incorrect, choice D. Is also incorrect. And so our correct answer will be choice be additive genetic effects occur when two or more genes make a single combined contribution to the final phenotype. See you in the next video.