AAMC Q bank Biology 2 #8

[sfsn]

What is this explanation saying?

I'm having trouble understanding the part of the explanation underlined in red below. I get everything else up to that point, and then my brain gets confused. I'm reading it as proteins are made, but then they could not have been produced? What do they mean by proteins of the P1 cells not being produced to carry the necessary message(s) to the AB cells prior to isolation?

The relevant portions of the passage are at the end.

Question
The results of Experiment 2 indicate that the signaling interaction at the two-cell stage probably most involves which class of molecule?

A. DNA
B. mRNA
C. rRNA
D. Protein

Explanation

Passage excerpt
Question is referring to the part of the figure in red (at least I'm pretty sure it is).

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[theonlytycrane]

good question- interested in this as well. If transcription is inhibited preventing production of mRNA, I'm wondering how signals are still sent from P1 to AB to produce neurons, skin, and muscle as normal.

 

[NextStepTutor_2]

What is this explanation saying?

I'm having trouble understanding the part of the explanation underlined in red below. I get everything else up to that point, and then my brain gets confused. I'm reading it as proteins are made, but then they could not have been produced? What do they mean by proteins of the P1 cells not being produced to carry the necessary message(s) to the AB cells prior to isolation?

The relevant portions of the passage are at the end.

Question
The results of Experiment 2 indicate that the signaling interaction at the two-cell stage probably most involves which class of molecule?

A. DNA
B. mRNA
C. rRNA
D. Protein

Explanation
View attachment 202748



Passage excerpt
Question is referring to the part of the figure in red (at least I'm pretty sure it is).

View attachment 202749

View attachment 202742

Hi @sfsn ! this is actually a very old Q from the pre-2015 AAMC exams that is still around. Unfortunately the explanation has not gotten any better. The question is asking you to analyze Exp 2 results so quickly remind yourself of the procedure:

To summarize:

AB cells grown in the presence of the translation inhibitor cycloheximide. These cells produced only neurons and skin but not the muscle cells figure 1 says AB cells also give rise to.

AB cells grown in the presence of the transcription inhibitor actinomycin. Checking figure 1 we can see that the resulting differentiation of neurons skin and muscle is normal differentiation.

These results of the experiment indicate that inhibiting transcription (actinomycin) did not affect cell differentiation, whereas inhibiting translation (cycloheximide) did.

Since the product of translation is protein, the inhibition of translation would result in no proteins being formed. According to the experiment 2 results, this loss of proteins apparently blocks cell-to-cell communication and thus changes the cells’ fate. This is what I think they are trying, poorly to get at in the final sentence. @theonlytycrane As to how, you should not waste time trying to figure it out, only focus on understanding and answering the question. Perhaps they mean that only partial inhibition takes place.. it does not matter. The MCAT is not a smart exam. It is a predictable, standardized test with its own rules. There is only 1 answer based on the experimental results given to you.


Hope this helps, good luck!