The correct answer is that the shells of clams and other mollusks dissolve when the pH becomes more acidic.
This is because the shells of clams and other mollusks are made of calcium carbonate that is dissolved in acidic conditions. The pH needs to be low to dissolve calcium carbonate into it. It takes few days to dissolve the shell completely.
Explanation:
A single nucleotide-pair substitution missense mutation causes a change of a single amino acid into another. Aa a result, the produced protein will have an almost normal sequence except for one amino acid.
On the other hand, a frameshift mutation changes the Open Reading Frame (ORF) of the ribosome. The ribosome moves along the mRNA every three nucleotides (codons) and translates them into amino acids that will form the nascent protein. If there is a frameshift mutation (an insertion or deletion of a number of nucleotides not multiple of three) the ribosome will "read" the mRNA differently and will identify different codons than the wild-type sequence, so a large number of amino acids will be different in the mutated protein.
