Which of these is NOT a step in cell specialization?

Cell replication refers to the process by which a cell makes an identical copy of itself, typically through the process of mitosis. While essential for growth and tissue repair, it is not a direct step in cell specialization.

In the context of cell specialization, the other processes are crucial. Cell proliferation involves the increase in cell number, which may provide the basis for further specialization. Cell-cell interactions are critical because they influence how cells respond to their environment and communicate with one another, guiding the ways in which they differentiate. Finally, cell differentiation is the process through which a generic cell undergoes a change to become specialized for a specific function, such as becoming a neuron or a muscle cell.

Therefore, while replication is necessary for maintaining populations of cells, it does not contribute to the specialization of cells into different types with unique roles.