Question

what may happen when a mutation changes the amino acid sequence of a protein?
the protein may become less effective, more effective, or altogether nonfunctional.
messenger rna may no longer be transcribed because codons change.
error detection mechanisms in the nucleus may remove the altered dna.
the protein may be considered a new allele, or variant form, of the gene.
messenger rna may identify altered proteins and remove them from the cell.

Explanation:

A mutation changing a protein's amino - acid sequence can affect its function. Proteins' functions depend on their structure (which is determined by amino - acid sequence). A change can make it less/more effective or non - functional. Messenger RNA is transcribed from DNA (not directly affected by protein mutation in this way). Error - detection in the nucleus acts on DNA (not protein - related here). A protein is not an allele (alleles are gene variants). Messenger RNA doesn't remove proteins.

Answer:

The protein may become less effective, more effective, or altogether nonfunctional.