What type of mutation occurs when a codon changes from UAU to UAA?

A change from the codon UAU to UAA represents a mutation that introduces a stop codon. UAU codes for the amino acid tyrosine, while UAA is one of the three stop codons (the others being UAG and UGA) that signal the termination of protein synthesis. This interruption in the translation process can lead to a truncated polypeptide chain, substantially impacting the resulting protein's function and overall stability.

In this context, the mutation is classified as a nonsense mutation because it converts a codon that codes for a specific amino acid into a stop codon. The consequence of such mutations is quite significant, often resulting in nonfunctional proteins or incomplete polypeptides, which can have varied effects on an organism's traits and health.

Understanding this type of mutation is crucial in genetics and molecular biology since it can help explain how certain genetic diseases arise when normal protein synthesis is disrupted.