I am a cell. I am long and thin. I reach all the way from the brain to the tip of a finger. I have a special coat of fat that helps me do
my job. My job is to send electrical signals from one part of the
body to another.

Neurons

Explanation:

We humans have a nervous system that coordinates our behavior and transmits signals between different parts of our body.

Now, this nervous system contains a lot of nerve cells which we call Neurons. These Neurons have a cell like body and their job is to transmit signals from one part of our body to another.

Thus, the cell is called Neurons.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).