From gene to peptide

You will turn the coding strand of a gene into messenger RNA, cut it into codons, and read the codons with a small table until a stop codon appears.

The idea. The mRNA has the sequence of the coding strand, with U in place of T. A codon is three bases. A peptide of $n$ amino acids has $n - 1$ peptide bonds.

Your tasks.

1. Complete transcribe(coding) so that it returns the mRNA.
2. Complete split_codons(mrna) so that it returns the list of codons.
3. Complete translate(mrna) so that it returns the list of amino acids, and stops at the first stop codon.
4. Complete peptide_bonds(peptide).