It is 4 long would the peptide be that is translate from this MRNA sequence 5'-AUGGGCUACCGA-3'. The MRNA sequence 5'-AUGGGCUACCGA-3' is 4 long that would the peptide be translate. The answer in this question is 4 (four). Messenger ribonucleic acid or MRNA is a type of RNA that you transcribe from a template of DNA.