A variety of pea plant called Blue Persian produces a ta...

Question

A variety of pea plant called Blue Persian produces a tall plant with blue seeds. A second variety of pea plant called Spanish Dwarf produces a short plant with white seed. The two varieties are crossed, and the resulting seeds are collected. All of the seeds are white; and when planted, they produce all tall plants. These tall F₁ plants are allowed to self-fertilize. The results for seed color and plant stature in the F₂ generation are as follows:
F₂ Plant Phenotype Number
Blue seed, tall plant. 97
White seed, tall plant 270
Blue seed, short plant 33
White seed, short plant 100
TOTAL 500

Which phenotypes are dominant, and which are recessive? Why?

Accepted Answer

Hi, everyone. Let's look at our next question. It says which of the following statements about complete dominance is true. So our answer choices are asking us about the effect of hetero Cygnus Jenna types with complete dominance on the phenotype. And about our film asking. So we'll come back to that. But let's start by just recalling from our content video, what distinguishes complete dominance. So I've just put up a little complete versus incomplete dominance. Complete dominance is characterized by the presence of the dominant allele masks, the recessive phenotype completely. So if you've got a copy of the dominant and recessive allele, the effect of the recessive valley on the phenotype is completely masked by the presence of the dominant allele. So we're just gonna highlight dominant a little masks, recessive phenotype versus incomplete dominance where the presence of the dominant and recessive alleles together results in an intermediate phenotype. So the classic example is um red and the red and white flowers where the presence of the red and the white together in a head results in a pink flower. So an intermediate phenotype rather than masking of a recessive trait by a dominant trait. So let's look through our answer choices and evaluate them with this in mind. Choice A says Hatteras, I guess genotype can have, can have the dominant phenotype. Well, this is true. When dominance is complete heterocyclic, it will have the dominant phenotype because the dominant allele completely masks the recessive phenotype. But let's keep on looking at other answer choices to be thorough here. Choice B says heterocyclic genotype can have the recessive genotype. Well, this would not be correct. Um Because the recessive phenotype is masked by the presence of the dominant allele, you would never see that incomplete dominance. Um You wouldn't see it usually an incomplete dominance either where you would expect an intermediate intermediate phenotype. Um You might see this if a trait has variable expressivity or different penetrates where someone could inherit the dominant aaliyah, but not actually express it, but it's not going to happen in terms of complete dominance. Choice C says heterocyclic genotype can have a unique genotype. Well, the unique phenotype would be characteristic of incomplete dominance where you have this intermediate phenotype that isn't the same as either parental genotype. So that's also not an answer choice since it doesn't describe complete dominance. And then finally, choice D says the presence of a recessive allele can mask the dominant allele. And of course, it's the other way around that the dominant allele masks the recessive allele. So D is not correct. So again, which of the following statements about complete dominance is true choice. A hetero ziggy's genotype can have the dominant phenotype. See you in the next video.

Key Concepts

Mendelian Inheritance

Phenotype and Genotype

Punnett Square

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