I think its called an Axon.
The
correct answer is a: genetically similar individuals who have been raised in
similar environments.
<span>For
example, monozygotic twins, who share 100% of their DNA that grew up in the
same home have the highest correlation of their IQs (correlation is 0.86). </span>
I'm not sure how exactly you wanted this question to be answered. You're either talking about the symmetry where animals would have two legs or two arms for example and thus producing a pair of each muscle on both sides of the body, or you're refering to the development of agonistic and antaonistic muscles where each of them served a different purpose; either extending or contracting.
