Does DNA have 5 nitrogenous bases? I believe they are 5 because Uracil is not the same thing as Guanine, because, first of all, uracil "replaces" thymine, not guanine. And second, uracil performs a range of functions that go far beyond "replacing" thymines at the time of transcription and translation. Am I right?

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    $\begingroup$ No. Uracil is present in RNA which is not the same as DNA. $\endgroup$
    – Roni Saiba
    Commented Jul 3, 2021 at 15:43
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    $\begingroup$ The Biology.SE community has agreed that questions that show little or no prior research effort are off-topic on this site as are "homework" questions unless you have shown your attempt at an answer. Please edit your question and tell us where you've looked for answers, what you do know about the topic, and where exactly you still have questions. Under researched questions may be subject to down-voting and closure. In particular, I have a found KhanAcademy to be a very helpful introduction to unfamiliar subjects. $\endgroup$
    – tyersome
    Commented Jul 4, 2021 at 0:34
  • $\begingroup$ Thymine is 5-methyl-uracil, and one way of remembering this is that THYMinE and METHYl are (almost, but not quite) anagrams. $\endgroup$
    – user338907
    Commented Jul 6, 2021 at 7:53
  • $\begingroup$ Uracil in DNA arises from the deamination of cytosine , and as such replaces C and not thymine. Thus a C-G base-pair is converted (by deamination) to a mutagenic U-G base-pair (and there are sophisticated repair mechanisms to fix this). See Uracil in DNA – occurrence, consequences and repair, for example $\endgroup$
    – user338907
    Commented Jul 6, 2021 at 9:45

1 Answer 1


It's a bit more complicated than that.

This wiki entry on nucleotides should help clarify things: Nucleotide

Diagram of chemical structure of bases, nucleosides, nucleotides, etc

I'm not sure what you mean by "...a range of functions..."

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    $\begingroup$ From How do I write a good answer? in the help center, Answer well-asked questions. Not all questions can or should be answered here. Please save your efforts for questions appropriate to this site. I also encourage you to delete your answers to such questions (e.g. homework questions like this) as giving them answers encourages more undesirable posts. This is also destructive to the learning process by rewarding lack of thought and effort on the part of students. Thanks. $\endgroup$
    – tyersome
    Commented Jul 4, 2021 at 0:38
  • $\begingroup$ For "It's a bit more complicated than that", you could reference Uracil in DNA – occurrence, consequences and repair. (Uracil in DNA arises from the deamination of cytosine) $\endgroup$
    – user338907
    Commented Jul 6, 2021 at 8:41
  • $\begingroup$ @user338907 I was attempting to provide a starting point for the questioner's research rather than a direct answer, as suggested by (at)tyersome (I may not have succeeded in doing so). $\endgroup$
    – Armand
    Commented Jul 6, 2021 at 8:55

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