Translation occurs at the ribosomes (which may be attached to endoplasmic reticulum). The ribosomes themselves are made of rRNA.mRNA carries the code for the polypeptide as it is complimentary to a strand of DNA in the nucleus. During translation at a ribosome, three bases on a string of mRNA (called a codon) codes for 1 amino acid in the polypeptide chain.tRNA at the ribsome carries the appropriate amino acid to a codon on the strand of mRNA. The adjacent amino acids can then form peptide bonds to form a polypeptide.