I’ve been working in the past two days on a lecture about DNA transcription. For those who don’t remember their basic biology, transcription is part of the process of getting from the genetic code in DNA to functional proteins in your body. How much do you remember about the genetic code? I will remind you of this much, there are quite a few numbers involved!

The basics:

There are 4 bases in DNA: A, T, C, G

There are 20 basic amino acids that make up proteins

A string of 3 DNA bases is equal to each amino acid (called a codon)


So, first of all, how many possible combinations of 3 DNA bases are there to make different amino acids: 64. Hmmm, that’s quite a bit more than the 20 needed for amino acids! Now, there are also 3 stop and 1 start codon, but that’s still only 24. So, there are redundancies (no, not British office redundancies!) where some amino acids have as many as 4 different combinations like this:

Did you also notice that most of the repeats have the same first two letters and a different third one? That means that a few mistakes could be made in the process of making proteins, and you would still get the right thing. Isn’t that cool? Okay. Well, that’s your science and math lesson for the day, how 4 in groups of 3 can make 20!


  • Ah, this looks vaguely familiar, from my undergrad molecular biology class.

    So the repeats generally have the same first two letters and a different third one… Is it more likely for some reason that a mistake would be made in the third one than in the first or second? Or could the amino acids just as easily have been constructed so that the second letter was the one that tended to be interchangeable?

    Eleni 6.May.2011 6:12 pm

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