Final answer:
The specialization of cells to perform specific functions is known as differentiation, which is a crucial part of development and involves changes in cell characteristics based on their unique genetic expression.
Step-by-step explanation:
The process of cellular specialization to perform particular functions is called differentiation. This is the process whereby all unspecialized cells become specialized to perform distinct functions. During development, differentiation is a key step, in which cells undergo major changes in size, shape, metabolic activity, and overall function to perform certain tasks in the body. Moreover, development includes not only differentiation but also growth and repair, both of which involve the specialization of cells. The uniqueness of each cell type despite having the same DNA is analogous to actors reading their own unique parts from the same movie script; each cell type 'reads' only the portions of DNA that are relevant to its own function. This is referred to as the unique genetic expression of each cell.