Find the amount of cytosine

[premedprincess26]

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I thought that we could calculate the amount of one base present if at least one percentage is given. Exam Krackers FL #2 Q #168 (last q of the third section) says that it cannot be determined. I was wondering if there was particular reason that it could not be determined in this case. I would have guessed 25% cytosine given that adenine is 25%.

The question is:
The section of VEGFR mRNA that anneals to the siRNA contains 25% adenine. What is the cytosine content of the siRNA sequence?

A. 25%
B. 37.5%
C. 75%
D. Cannot be determined.

The correct answer is D

 

[wizzed101]

Only if you have double stranded DNA/RNAs in their entirety. A single strand will not tell you anything unless you have 3 of the 4 bases available.

Think about it this way. Is there any evidence/proof to contradict my assumption that there was no cytosine in the siRNA sequence?