Combination problem for AA sequence

Started by Ashish
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Ashish

Full Member
7+ Year Member
So if there area 5 different AA in a polypeptide, what is the possible number of sequence of nucleotide?

Different sources say it is 5!= 120 but I don't understand why?

Thank you!
 
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Roy Williams said:
It's a permutation. Same kind you should be studying for the QR section. 5P5 = 5!/(5-5)! = 5! = 120

If you have any other questions about this kinda stuff let me know!
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Three nucleotide makes 1 AA though and there are wobble bases where the 3rd of the 3 does not matter so first 2 really produces a unique AA. How do you incorporate this?
 
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What do you mean three nucleotides makes an amino acid? I was always under the impression that three nucleotides made a codon which codes for an AA. When the question says what is the possible number of sequences of nucleotides, I interpreted that as each sequence being a set of three nucleotides. So in general it was just asking how many ways can you arrange the 5 amino acids.
 
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gangazi said:
Draw 5 boxes
First box -- 5 diff AA can fill
second box -- 4 other diff AA ( excluding the one that filled the first one)

Do this until 5th box you got
5*4*3*2*1
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This makes sense.
Roy Williams said:
What do you mean three nucleotides makes an amino acid? I was always under the impression that three nucleotides made a codon which codes for an AA. When the question says what is the possible number of sequences of nucleotides, I interpreted that as each sequence being a set of three nucleotides. So in general it was just asking how many ways can you arrange the 5 amino acids.
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I meant combination of three bases makes 1 codon. I see what is going on here more clearly now. I was making things more complicated by considering the sequence of bases rather than just 5 distinct AA. Thanks.
 
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