Questions from AAMC5: Genetics and Waves

[ioud]

---

Members don't see this ad.

AAMC 5 #112 (Passage based question):
In a mating of two tetrahymena strains that are homozygous in their macronuclei and heterozygous in their micronuclei for a recessive gene, what percentage of the F1 generation will express the recessive phenotype?

Answer: 25%

Answer explanation: The macronuclei do not participate in mating so only the genotypes of the micronuclei need to be considered. Cross Rr x Rr to get F1.

After reading the explanation, I still can't understand why they crossed Rr x Rr. I thought it would be rr x Rr.

AAMC 5 #45
For a given laser cavity mode, the standing wave pattern within a laser cavity can be viewed as a superposition of two traveling waves. Their amplitudes and directions are described by which of the following?

Answer: equal amplitudes, opposite directions

Physics is my weak area and I just don't understand how the waves have equal amplitudes when there is a superposition.

Can someone please explain these two problems?
Thank you

 

[wolverine1]

AAMC 5 #112 (Passage based question):
In a mating of two tetrahymena strains that are homozygous in their macronuclei and heterozygous in their micronuclei for a recessive gene, what percentage of the F1 generation will express the recessive phenotype?

Answer: 25%

Answer explanation: The macronuclei do not participate in mating so only the genotypes of the micronuclei need to be considered. Cross Rr x Rr to get F1.

After reading the explanation, I still can't understand why they crossed Rr x Rr. I thought it would be rr x Rr.

AAMC 5 #45
For a given laser cavity mode, the standing wave pattern within a laser cavity can be viewed as a superposition of two traveling waves. Their amplitudes and directions are described by which of the following?

Answer: equal amplitudes, opposite directions

Physics is my weak area and I just don't understand how the waves have equal amplitudes when there is a superposition.

Can someone please explain these two problems?
Thank you

#112: Well, the passage states that the macro nuclei do not participate in the mating process. Thus, the heterozygous ones are the active ones. Rr x Rr. I'm not sure where you get rr because it clearly says homozygous does not participate.

#45: I think superposition means that they overlap. When two waves overlap, they should have the same amplitudes. I don't, however, know why they are traveling in opposite directions. Someone check me.

Hope that helps.

 

[ioud]

how did you infer that the macronuclei is homozygous and the micronuclei is heterozygous?

thank you for answering my question🙂

 

[ODorDO]

I was wondering the same thing too! how do you know marconucle is not in this?? these little facts always bite me in the rear

 

[Vanguard23]

how did you infer that the macronuclei is homozygous and the micronuclei is heterozygous?

thank you for answering my question🙂

From your quote?
"In a mating of two tetrahymena strains that are homozygous in their macronuclei and heterozygous in their micronuclei for a recessive gene, what percentage of the F1 generation will express the recessive phenotype?"

 

[traitorman]

I had a question about this same passage. In the passage it says that the macronucleus is the site of gene expression in the vegetative state. So if two Tetrahymena strains are homozygous in their macronucleus for the recessive gene, shouldn't the answer be 100% of the F1 generation will be expressing the recessive phenotype?

 

[sudo]

Can someone tell me how you know that "the macronuclei do not participate in mating"?

I'm having trouble deducing that from the passage 😡

 

[folktale]

I missed the problem 45 for that exact same reason too. I never really saw where in the passage states that the macronuclei does not participate, so I crossed macro with micro.

 

[pfaction]

Yeah it was stated in the top passage or such in the middle that only ONE of them contribute to genetics, the other one was purely proteins and whatever else.

Standing waves: imagine a sine wave. Now flip it in the middle to make the two nodes touch. There's a standing wave. Opposite directions, straight reflection, so different directions but same amplitude.

 

[sudo]

Yeah it was stated in the top passage or such in the middle that only ONE of them contribute to genetics, the other one was purely proteins and whatever else.

Standing waves: imagine a sine wave. Now flip it in the middle to make the two nodes touch. There's a standing wave. Opposite directions, straight reflection, so different directions but same amplitude.

I've reread the passage so many times and can't make the connection 😡

 

[plee]

This might be kind of late, but im just doing these practice exams now.

2 nuclei: a diploid germ-line micronucleus
4-5ploid macronucleus for gene expression blahblah.

germ-line = only thing passed down.