Answer:
Genes.
Explanation:
The cells make up the complete system of all living thing. They contain the DNA or deoxyribonucleic acid, which in turn contains the gene where the code for a specific protein that functions on a part in a cell.
There are three types of genes, they are;
Body plan gene, body patterning gene and proteincodins.
Gene switch is the process where genes go on and off.
The body plan and patterning genes for limbs in snakes and manatees have been switched off due to evolution.
