Question

Beta cells in the pancreas and human skin cells
both contain the insulin gene. The beta cells can
make insulin; however, skin cells cannot. Which
process is responsible for this gene being
expressed in one cell type and not in another
cell type?
(1) mitosis (3) differentiation
(2) replication (4) meiosis

Answer 1

(3) differentiation 
In this process, the zygote, through the process of mitosis, becomes a muticellular organism where over time, the cells' DNA activate certain genes to express certain traits leading to the formation of tissues, then organs and even more complex structures resulting the formation of a fetus.