Which of the following would produce a silent mutation?
a. the deletion of a single base.
b. the replacement of a single base, producing a stop codon.
c. the replacement of a single base, producing the same amino acid.
d. the insertion of a single base.

C

Explanation:

A silent mutation is a mutation that does not have an observable change or effect on the organism bearing it. If a base in a DNA sequence changes but the new codon codes for the same amino acid (remember amino acids translation have redundancies), then they will be no observable effect. The most lethal kind of mutation is deletion and insertion because they result in a frameshift mutation.

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.