A geneticist from an alien planet that prohibits genetic research...

Question

A geneticist from an alien planet that prohibits genetic research brought with him to Earth two pure-breeding lines of frogs. One line croaks by uttering 'rib-it rib-it' and has purple eyes. The other line croaks more softly by muttering 'knee-deep knee-deep' and has green eyes. With a newfound freedom of inquiry, the geneticist mated the two types of frogs, producing F₁ frogs that were all utterers and had blue eyes. A large F₂ generation then yielded the following ratios:

27/64 blue-eyed, 'rib-it' utterer
12/64 green-eyed, 'rib-it' utterer
9/64 blue-eyed, 'knee-deep' mutterer
9/64 purple-eyed, 'rib-it' utterer
4/64 green-eyed, 'knee-deep' mutterer
3/64 purple-eyed, 'knee-deep' mutterer

Assign gene symbols for all phenotypes and indicate the genotypes of the P₁ and F₁ frogs.

Accepted Answer

Hi all. Let's look at our next question. It says a geneticist cross fertilized the different p plants that different only one character to produce F. One offspring. He then allowed the F. 1 to self fertilize to raise the F two generation. The following ratios were then obtained from a large f. two generation. And we have four different possible ratios listed here in four different statements. And then our question says assuming that the alley for tall Nous Capital T. Is dominant over the alcohol for shortness. Little T identify the option. That includes the offspring with both parents being hetero sickos for one treat. But we kind of don't even need to worry about the parents of the F. One generation. We're looking for. What ratio would we expect for offspring of two hetero sickos parents. So since our gene here that we're looking at is for tall Nous. We expect the parents will then be big T. Little T crossed with big T. Little T. When we have a mono hybrid cross like this we expect to see a fanatic ratio of three 2 1 in terms of the dominant phenotype to the recessive phenotype. So we'd expect to see about 75% of the offspring showing the dominant trait of tall nous and about 25% to be short. So let's look here at our various ratios to see which corresponds with that Statement. P has 52, tall too short. Well that's approximately ratio of 1-1 which is not expected 3-1 ratio. So we'll eliminate p. Que has 78 tall to 26 short, which is About a 75% 25% ratio. So we're going to say that Q definitely reflects parents who are heterosexuals for the treat. That statement are has 99-0 tall too short. Well that would definitely not be what we would expect in a cross of two hetero cigarettes. We would not expect to see all of them being tall and none of them being short. So eliminate our S. is the reverse zero tall to 77 short. Again, definitely not what we expect to see in a cross of two heterocyclic. It's so eliminate us. So as we look down our answer choices, we would say that only Q 78 to 26 tall two short reflects our expected outcome With parents who are both Hetero Zig. It's 3-1 ratio, dominant recessive. So choice B. Q. Only is the answer we're looking for here. See you in the next video

Key Concepts

Mendelian Genetics

Phenotype and Genotype

Punnett Squares and Ratios

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