DNA to Protein Python Function

Question

I'm a huge Python noobie trying to finish my code of translating DNA to RNA to Protein - it should start printing proteins once the 'Met' protein is found, and stop printing once the 'STOP' proteins are found, and I want it to return a list of strings. But somehow it ONLY prints ['Met'] when this DNA string is included? I wonder where I'm going wrong...

e.g. translate('AAATACGTATTA') should return ['Met', 'His', 'Asn'].

def transcribe(str):

    dna = 'ATGC'
    rna = 'UACG'
    transcription = str.maketrans(dna, rna)
    return (str.translate(transcribe))

def translate(dna):

    codon_list = {'UUU':'Phe','UUC':'Phe','UUA':'Leu','UUG':'Leu','CUU':'Leu','CUC':'Leu',
       'CUA':'Leu','CUG':'Leu','AUU':'Ile','AUC':'Ile','AUA':'Ile','AUG':'Met',
       'GUU':'Val','GUC':'Val','GUA':'Val','GUG':'Val','UCU':'Ser','UCC':'Ser',
       'UCA':'Ser','UCG':'Ser','CCU':'Pro','CCC':'Pro','CCA':'Pro','CCG':'Pro',
       'ACU':'Thr','ACC':'Thr','ACA':'Thr','ACG':'Thr','GCU':'Ala','GCC':'Ala',
       'GCA':'Ala','GCG':'Ala','UAU':'Tyr','UAC':'Tyr','UAA':'STOP','UAG':'STOP',
       'CAU':'His','CAC':'His','CAA':'Gln','CAG':'Gln','AAU':'Asn','AAC':'Asn',
       'AAA':'Lys','AAG':'Lys','GAU':'Asp','GAC':'Asp','GAA':'Glu','GAG':'Glu',
       'UGU':'Cys','UGC':'Cys','UGA':'STOP','UGG':'Trp','CGU':'Arg','CGC':'Arg',
       'CGA':'Arg','CGG':'Arg','AGU':'Ser','AGC':'Ser','AGA':'Arg','AGG':'Arg',
       'GGU':'Gly','GGC':'Gly','GGA':'Gly','GGG':'Gly'}

    rna = translate(dna) 
    sequence_num = len(rna) 
    protein_start = 0

    for i in range(sequence_num):
        if(rna[i:i+3] == "AUG"):
            protein_start = i
            break

    protein = []
    for i in range(protein_start, sequence_num, 3):
        codon = codon_list[rna[i:i+3]]
        if (codon == "STOP"):
            break
        elif (codon == "Met"):
            protein.append(codon)
            return protein

Thank you :)

The formatting of your posted code seems off. Can you update it, for indentation and to be a complete running example? That's the best way to get help with your issue. — Gary02127

Frank Yellin Frank Yellin · Accepted Answer · 2021-10-17T05:01:05

    for i in range(protein_start, sequence_num, 3):
        codon = codon_list[rna[i:i+3]]
        if (codon == "STOP"):
            return protein // or a break statement if more code
        else:
            protein.append(codon)

DNA to Protein Python Function

1 Answers