Question

what type of mutation causes premature stop codons?
nonsense mutations
distance mutations
missense mutations

Explanation:

Nonsense mutations change a codon that normally codes for an amino - acid into a stop codon, leading to premature termination of protein synthesis. Distance mutations are not a standard term related to stop - codon formation, and missense mutations change one amino - acid to another, not create a stop codon.

Answer:

nonsense mutations