DNA/RNA question

[nickelbackfan]

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DNA is more stable than RNA, making DNA a better molecule for the storage of genetic information. Which of the following statements supports the idea that DNA is more stable than RNA?

I. DNA lacks a hydroxyl group at the 2' carbon atom, making the polymer less susceptible to hydrolysis.
II. DNA is a double-stranded molecule, while RNA is found primarily as a single-stranded species.
III. DNA uses thymine instead of uracil as a nitrogenous base.



Answer is all three. I dont understand why III contributes to DNA being more stable. Thymine and uracil are pretty similar in structure.

Answer explanation for III is

The use of thymine in DNA instead of uracil also adds to the stability of the DNA helix. The hydrogen-bonding properties between adenine and thymine are a little more stable than the hydrogen-bonding properties between adenine and uracil. Remember, we can have hydrogen-bonding between adenine and uracil. Where? Recall that as the RNA polymerase enzyme transcribes the DNA into mRNA, there is a region on the DNA template strand where we find DNA/RNA hybridization. If there happens to be an A in the template strand, then that A will be hydrogen-bonded to a U in the mRNA strand.

 

[Trayshawn]

Where did you get this question? The AAMC? Because I disagree wholeheartedly.

The only difference between thymine and uracil is a lowsy methyl group!

Answer choice I MUCH better explains the relative STABILITY of DNA. Its less susceptible to hydrolysis!
The other choices are just known differences, not explanations of better stability.

 

[nickelbackfan]

Where did you get this question? The AAMC? Because I disagree wholeheartedly.

The only difference between thymine and uracil is a lowsy methyl group!

Answer choice I MUCH better explains the relative STABILITY of DNA. Its less susceptible to hydrolysis!
The other choices are just known differences, not explanations of better stability.

TBR CBT 6

I have noticed that a handful of there questions are really debatable. I know im not a authoritative figure but I think there are some errors in other questions as well which kind of degrades there creditable in my eyes. I wanted to see what you guys think

 

[circulus vitios]

Where did you get this question? The AAMC? Because I disagree wholeheartedly.

The only difference between thymine and uracil is a lowsy methyl group!

Answer choice I MUCH better explains the relative STABILITY of DNA. Its less susceptible to hydrolysis!
The other choices are just known differences, not explanations of better stability.

Exactly what I was going to say. What a terrible question.

 

[richkaj]

It would have made sense if they put nucleoside or nucleotide whereby it includes the sugar moiety as well or say thymidine vs uridine... Good eyes 0-0

 

[sciencebooks]

DNA is more stable than RNA, making DNA a better molecule for the storage of genetic information. Which of the following statements supports the idea that DNA is more stable than RNA?

I. DNA lacks a hydroxyl group at the 2' carbon atom, making the polymer less susceptible to hydrolysis.
II. DNA is a double-stranded molecule, while RNA is found primarily as a single-stranded species.
III. DNA uses thymine instead of uracil as a nitrogenous base.



Answer is all three. I dont understand why III contributes to DNA being more stable. Thymine and uracil are pretty similar in structure.

Answer explanation for III is

The use of thymine in DNA instead of uracil also adds to the stability of the DNA helix. The hydrogen-bonding properties between adenine and thymine are a little more stable than the hydrogen-bonding properties between adenine and uracil. Remember, we can have hydrogen-bonding between adenine and uracil. Where? Recall that as the RNA polymerase enzyme transcribes the DNA into mRNA, there is a region on the DNA template strand where we find DNA/RNA hybridization. If there happens to be an A in the template strand, then that A will be hydrogen-bonded to a U in the mRNA strand.

I also wouldn't have known that III necessarily contributes to stability, but if the information in the explanation is true, then obviously it would. I don't remember learning that in any of my MCAT studies though...

 

[Anthrax]

This questions seems to ask way more detailed knowledge than what I have seen in the AAMCs.

Yes, we should know the number of H-bonds between complimentary bases but I have never seen a question that requires you to know structural differences between individual bases. Maybe between purines and pyrimidines but never differences like methyl groups or Hs on bases.