Final answer:
Cellular differentiation is the process by which cells become specialized in structure and function, similar to actors only reading their parts of a script. This differentiation is lacking in cancer cells, which instead continue to divide uncontrollably without acquiring specialized functions. Therefore, the correct option is 1.
Step-by-step explanation:
The process by which cells acquire their specific structure and function is referred to as cellular differentiation. This is a critical aspect of development, growth, and reproduction, in which unspecialized cells become specialized in their structure and function to perform certain tasks within the body. Similar to how actors in a movie read only their part of the script, each cell in the body contains the full complement of DNA but only 'reads' or expresses the portions relevant to its function. Cancer cells often exhibit a lack of differentiation, meaning they do not acquire the specialized functions typical of healthy cells and instead continue to divide uncontrollably.
During cellular differentiation, a number of changes occur such as alterations in size, shape, and metabolic activity which lead to cells with unique morphological and physiological characteristics dictated by the expression of certain genes, under the influence of transcription factor proteins. This specific gene expression results in the diversity of cell types found within the human body. In contrast, cancerous cells tend to be 'generic' and lack the ability to perform specialized body functions because they do not undergo proper differentiation.