AAMC Exam 7 Bio question (specific spoiler)

[DontBanMeBro]

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Hello

Passage 7 about the 2 cell embro with AB and P1 cells differentiating into muscle, gut, nervous cells etc.

Experiment 2

Two‑cell embryos were incubated in the presence of either cycloheximide, an inhibitor of translation, or actinomycin D, an inhibitor of transcription. The AB cells were then isolated, washed to remove the inhibitors, and grown in culture. AB cells from embryos treated with cycloheximide produced only neurons and skin, whereas those from embryos treated with actinomycin D produced neurons, skin, and muscle

Question:
The results of experiment 2 indicate that the signaling interaction at the two cell stage is most likely due to which class of macromolecules?

Answer is protein.

now, my question is, why is it protein? The first group of cells could make mRNA but not protein. The second group could not make mRNA and therefore no protein. So basically neither group of cells had protein. Should it not be mRNA? Let me add that the correct differentiation occurred in the second group because they are supposed to become nerve, muscle, and skin

 

[fedoraenglish]

I just finished this exam. Cyclohex prevents translation in P1s. When the other drug (actinomycin) was used, it did not affect P1 transcription. When the translation of P1 is disrupted, that's when you have a problem with muscle development. Thus, it is protein that is most important (a product of translation).

Sorry if my response didn't make sense. I'm super tired and my mcat is on the 9th. I tried to re-open the exam to read why my answer was correct but they wanted me to re-do the whole thing so I just explained to you how I reasoned it out based on what you pasted above. Hope this helps.

 

[sunflower18]

Hello

Passage 7 about the 2 cell embro with AB and P1 cells differentiating into muscle, gut, nervous cells etc.

Experiment 2

Twocell embryos were incubated in the presence of either cycloheximide, an inhibitor of translation, or actinomycin D, an inhibitor of transcription. The AB cells were then isolated, washed to remove the inhibitors, and grown in culture. AB cells from embryos treated with cycloheximide produced only neurons and skin, whereas those from embryos treated with actinomycin D produced neurons, skin, and muscle

Question:
The results of experiment 2 indicate that the signaling interaction at the two cell stage is most likely due to which class of macromolecules?

Answer is protein.

now, my question is, why is it protein? The first group of cells could make mRNA but not protein. The second group could not make mRNA and therefore no protein. So basically neither group of cells had protein. Should it not be mRNA? Let me add that the correct differentiation occurred in the second group because they are supposed to become nerve, muscle, and skin

The way I thought about it was that the second group probably had some old mRNA hanging out that had been transcribed prior to the experiment, and this previously made mRNA could still make protein. However, the first group can't make protein at all, no matter what the situation of transcription was prior to the experiment.

This might have been an incorrect way to think about it, but it worked for this question.

 

[sector9]

Closing thread as the OP has been banned.