Observe the following reactions (not balanced):
Cl2 + NaOH → NaCl + X + H2O
Cl2 + NaOH → NaCl + Y + H2O
\( +1, \, +5 \)

In a messenger RNA molecule, untranslated regions (UTRs) are present at:
I. 5' end before start codon
II. 3' end after stop codon
III. 3' end before stop codon
IV. 5' end after start codon