*SPOILER* Section Bank C/P #80

[Dr. To Be]

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Hi all!


I'm confused as to how the answer here is C. I thought the answer should be B because ( with my counting) isn't there 6 hydrogen bond acceptors? I thought Cytosine would have 4 hydrogen bonds. Any help is appreciated =)

 

[aldol16]

They're not talking about total H-bond donors and acceptors. They're talking about those that are available to H-bond when involved in a Watson-Crick base pair. Take a look at this figure and count again: http://www.education.mrsec.wisc.edu/132.htm

 

[sazerac]

If you go to Wikipedia and look up the DNA article, the first picture shows the hydrogen bonds of AT and CG. It should be pretty obvious then.

 

[Dr. To Be]

Wow! I completely missed "Watson-Crick base pair". Thanks everyone!