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I don't understand this question, hoping someone can help!

One of the following bases does not belong among pyrimidine bases: - Uracil - Adenine - Cytosine - Thymine

I thought that everyone was bases, expect that uracil is in RNA, and that in DNA it is replaced by guanine.

Also one more question: Which of the processes would never contribute to genetic variation within a bacterial population? - Transformation - Meiosis - Mutation - Transduction

I have a hunch that the right answer is mutation, but I don't know why. If you know the answer, it would be very helpfull if you could explain why :-)

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    $\begingroup$ Welcome to Biology.SE. A post should never contain more than one question. As such, the post should be closed as too broad. Also, homework question requires that the OP shows its effort at answering the question. Typically, for the first question, it really is just a matter of googling pyrimidine. You can have a look at our policy about homework questions here. $\endgroup$
    – Remi.b
    Mar 5, 2017 at 18:13
  • $\begingroup$ I'm really sorry for breaking your policy! I thought that by asking more than one question I was being efficient for both myself and the ones answering. You're absolutely right about the first question - but stress can be paralyzing. I will follow the rules from here on. $\endgroup$
    – Thomas
    Mar 5, 2017 at 20:08
  • $\begingroup$ No worries. It takes a few posts to get used to the SE policies, formatting and things. After that, it is in my opinion a fantastic tool to be using during your studies. $\endgroup$
    – Remi.b
    Mar 5, 2017 at 20:12

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You are correct - they are all bases. However there are two types of bases. Purines and pyrimidine bases. Purines have two ring systems, while pyrimidines have only one. With this hint, I think you will be able to find the answer to your first question.

As for your second question. Can you give me a definition for what a mutation is? I think if you are able to define this word you will know why that answer is incorrect.

Also, bacteria are incapable of performing one of the four processes that you have listed - and that particular process, is therefore the correct answer to your second question.

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  • $\begingroup$ Thank you for your detailed and very pedagogic answer. Forgive me for being a total newbie, but as far as I can see both guanine and adenine are pyrines? Mutation are permanent changes in the DNA. So it could contribute to genetic variation.... but bacterias are incapable of meiosis, of course! $\endgroup$
    – Thomas
    Mar 5, 2017 at 20:13
  • $\begingroup$ Yes, guanine and adenine are purines. And bacteria are incapable of meiosis. Well done. But, one last thing, it is actually thiamine that is replaced by uracil in RNA; and not guanine as you stated in your question. $\endgroup$
    – Bob
    Mar 5, 2017 at 21:29
  • $\begingroup$ So the correct answer to the first question is adenine (I mixed up guanine as one of the alternatives, as you may have guessed ;-). Thank you for clearing up my RNA mix-up as well. $\endgroup$
    – Thomas
    Mar 5, 2017 at 21:45

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