Select the three correct answers. nucleotide substitutions within a coding sequences always change the amino acid sequence encoded by a gene. mutations that occur in the intron sequences cannot affect the protein coding sequence of a gene. missense mutations always change the amino acid sequence encoded by a gene. insertions or deletions of single base-pairs within a protein coding sequence probably change the amino acid sequence encoded by a gene. nucleotide substitutions outside of the coding sequence can affect the expression of a gene.