Final answer:
The start codon in mRNA for translation is AUG. It specifies methionine and marks the beginning of translation.
Step-by-step explanation:
The start codon in mRNA for translation is AUG. This codon specifies the amino acid methionine and also marks the beginning of translation. It establishes the reading frame of the mRNA, with the next three letters after the start codon being read as the second codon, and so on until a stop codon is reached. Stop codons, such as UAG, UGA, and UAA, do not code for any amino acids and are known as termination codons.