Answer:
A
Explanation:
The reason the deletion of a nucleotide can be a lethal mutation is that it causes a frameshift mutation. This is due to teh fact that the codon sequence on the DNA is shifted by a single nucleotide. Therefore, the codons will read differently downstream from the place the deletion happened. The amino acids coded for by these codons will change too. The translated proteins will be defective and the organisms will be adversely affected, phenotypically.
