How do different cell types arise from the same DNA?

Different cell types arise from the same DNA through a process known as gene expression regulation, in which environmental signals and developmental cues activate or deactivate specific sections of the DNA. This means that while all cells within an organism contain the same genomic information, they can express different sets of genes to assume distinct functions.

For example, in a multicellular organism, stem cells can differentiate into various specialized cells—like muscle cells, nerve cells, or skin cells—based on the signals they receive from their environment and from surrounding cells. These signals can promote or inhibit the expression of certain genes, leading to the production of specific proteins that define the characteristics and functions of different cell types.

In contrast, the other options do not adequately explain this phenomenon. Mutations in DNA can contribute to variability, but they do not solely account for the diversity of cell types in a multicellular organism. Similarly, the notion that cells randomly change their functions does not reflect the regulated and orderly process that governs cell differentiation. Lastly, the idea that all cells have identical roles suggests uniformity and fails to recognize the specialization that exists within complex organisms. Therefore, the regulation of gene expression in response to environmental signals is the fundamental mechanism through which different cell types arise from the same DNA.