Final answer:
Cells differentiate because they express different sets of genes despite having the same DNA. Transcription factors regulate which genes are expressed, leading to specialized cells with unique functions and structures.
Step-by-step explanation:
The Cause of Cell Differentiation
The cause of cell differentiation lies not in the presence of different DNA or chromosomes, but rather in the unique way that each cell expresses its genetic information.
Despite all cells in a multicellular organism containing the same DNA, they become specialized by expressing a different set of genes, which lead to variations in size, shape, metabolic activity, and function. This process is similar to actors in a movie reading from the same script but only performing their specific parts.
Gene expression is regulated in part by transcription factors, which bind to DNA and either promote or hinder the transcription of different genes. Hence, even though every cell has the same genetic information, each type specializes by expressing only a subset of the available genes that dictate their unique functions and structures.
It is important to note that cells differentiate by turning on new genes and turning off old ones, a mechanism that involves the regulation of gene products during differentiation.
Thus, all somatic cells contain the same genome; however, they differentiate by altering which genes they actively express. This gene regulation results in a diversity of cell types, each with its morphological and physiological characteristics, despite the universal DNA blueprint.