Answer:
A mutation in the DNA sequence of the gene for brown fur
Explanation:
The mutations are capable of changing the encoded protein product, in this case the gene that encodes for the fur color pigment. This mutation may have occurred during mitosis or meiosis divisions.
If it is a spontaneous mutation that occurred in the germinal line (meiosis) and confers an adaptive advantage, it will increase their frequency in the population.
The answer is Sodium Chloride
