Amino acids question

i think this is a really simple question but im missing a small point, why do we say 20 amino acids for this one?


first you have to transcribe only ONE strand of DNA to make mRNA, then translate it into proteins
so 60/3=20 AA
My question is why is it 20 not 18? here the 120 nucleotides are for the DNA strand, so why aren’t we subtracting the start and stop codon??? We can’t make a polypeptide from DNA if we don’t have them?

(although yes the start codon is a methionine protein and the stop codon can code for selenocysteine protein making 20AA, which we’re not supposed to know for the IMAT, i might be overthinking the question, if anyone has feedback please let us know!)


i would include the start codon as it already transcribes for something but I’m not sure about the stop codon. maybe they just considered it 20 and did not specify the details.


excuse me , just for the sake of clarification, are we not supposed to take the methionine protein codon into account when solving these questions? I mean the IMAT exam itself

Most proteins start with methionine, but some have them removed afterwards (post-translational modification).

So, I hope the questions will not be so tricky:D but if we are asked about how many amino acids are translated directly from ribosomes, I would include methionine as well.


but for the stop codon should i not care about it or take it out as well because it doesn’t code

the stop codon does not translate into any amino acid, so in case we are asked about the number of amino acids coded for by the whole mRNA strand, do not include it.