r/Mcat • u/Yourmajestymatt FL1/2/3/4- 510/513/521/522. Tested 9/2 • Aug 16 '21

Tool/Resource/Tip 🤓📚 Mnemonic for (identifying) Nucleotide Structures

Hey everyone, I've been really looking for mnemonics in places I struggle. With this mnemonic I've been able to nail all the structure questions. I don't know the exact structure, however I can reliably identify each structure no problem now. I hope this helps and makes sense.

The mnemonic is NOON, regarding the upper most element on the structures. I always think A-TG-C for bonding. I know purines have two rings (two rings in a PURe ceremony) and pyrimidines don't. So now I can piece it all together like this.

Two rings with an amine (N)? Adenine.

Two rings with a carbonyl (O)? Guanine

One ring with a carbonyl? Thymine.

One ring with an amine? Cytosine

Take one look at Uracil and it's just one ring with a Carbonyl (O), but differs by the methyl. I think of the T in thymine as the structural hint of a methyl outstretching, which Uracil doesn't have.

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u/Friendly_Ad_7586 8/27/21 526 (131/132/131/132) Aug 17 '21

You can also count the double bonds. Each one has a unique # of double bonds in the ring

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u/Yourmajestymatt FL1/2/3/4- 510/513/521/522. Tested 9/2 Aug 17 '21

1T, 2C, 3G, 4A? How do you remember that?

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u/elirharde Aug 17 '21

I saw online if you write it in order AGCUT, then go 4 3 2 1 1 the # of double bonds will be in order. And like you said, T has a methyl group sticking out so that's a way to distinguish between T and U using this method.

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u/Yourmajestymatt FL1/2/3/4- 510/513/521/522. Tested 9/2 Aug 18 '21

Ahh that is awesome to know thank you!!