When a cell divides by way of mitosis, it produces two clones of itself, each with the same number of chromosomes. When a cell divides by way of meiosis, it produces four cells, called gametes. Gametes are more commonly called sperm in males and eggs in females.
Our nervous system runs on chemical synapses ! that means we need chemical to transfer information from one neuron to another !
so when the signal reaches the synaptic knob of one neuron , it stimulates the neurotransmitters containing vacuoles to release the neurotransmitters !
the neurotransmitters may be dopamine, acetylcholine etc and after reaching the dendrites of other neuron, it stimulates signal in the other neuron and thus a signal travel from one part of body to other !
No, the vast majority of DNA mutations are not physically noticeable, and those that are noticeable physically are mainly cosmetic differences, such as a change in hair color, or heterochromia.