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Old 03-24-2010
Yallah's Avatar
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Molecular Cellular RNAs?

Which of the following most affects expression of specific cellular RNAs in fast growing liver cells of an infant?
A- Mitochondrial protiens
B- Vitamins
C- Nuclear transcription factors
D- Ribosomes
E- Peroxisomal proteins

Am puzzled with this
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Old 03-24-2010
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The question stem indicates a condition of intense gene expression. In all probability the correct answer is either C or E. Let's follow a stepwise strategy for this one.

A. Mitochondrial proteins have mainly to do with the processes taking place within the mitochondria, such as oxidative phosphorylation. Also keep in mind that even proteins related to the transcription of the mitochondrial DNA largely derive from the nuclear genetic material.

B. Lipid soluble vitamins may have the same structure as steroids, but their role is rather modulating than directly transcriptive (i.e. they act as ligands to receptors, they are not transcripiton factors themselves). If this helps, remember the role of a vitamin A derivative, all-trans retinoic acid, in the therapy of M3 subtype of AML.

D. Ribosomes are related to protein synthesis, not RNA synthesis.

E. If by the term "peroxisomal proteins" the author hides a hint for PPARs, then you have a kind of transcription factor involved in gene expression. However, I don't think this is the case here. In all probability, with the term "peroxisomal proteins", the author indicates those proteins that are specifically targeted for degradation within the lysosome. This process has to do with proteins targeted to get out of the cell or to be integrated within the cell membrane.

To conclude with, I think that the only group of molecules that are related to the expression of RNA in a fast growing population of cells are nuclear transcription factors. Please make your comments and any suggestions if the abovementioned justification is not rational.
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Old 03-24-2010
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I agree with you and thank you for such a great break down of the options.
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Old 03-24-2010
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Default Correct

Yes, you are right.
PPARs are transcription factors useful for cellular differentiation and metabolism (such as fatty acids) and NOT for reproductive tasks such as that in a rapidly dividing cell.
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Molecular-Biology-, Step-1-Questions

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