Answer:
1, 2 and 3
(1) Translation always begins with an AUG start codon.
(2) The start codon establishes the reading frame of mRNA.
(3) The mRNA molecule is read one codon at a time until a stop codon is reached.
Explanation:
Translation is the second stage of the gene expression process which involves the synthesis of amino acid sequence (protein) from an mRNA transcript. During translation, the nucleotide sequence are read in a group of three nucleotides called CODON. The codon are found on the mRNA molecule and each one specifies an amino acid.
Translation starts with a start codon, which is AUG coding for methionine. Due to the fact that translation will start with an AUG codon, it automatically sets the reading frame of the mRNA molecule i.e. the pattern the mRNa will be read during translation. The start codon (AUG) determines how the reading frame will progress considering it is read first or initiates the translation process.
Translation continues in the RIBOSOME, where each codon is read by the tRNA one at a time until a stop codon is encountered. A stop codon signals the end of the translation process, and releases the peptide sequence. The mRNA stop CODON specifies no amino acid and are UAG, UAA, and UGA.
