How can cells with the same DNA become muscle cells or neurons?

Although all cells in an organism contain the same DNA, they become specialized—such as muscle cells or neurons—through a process called cell differentiation. This process does not involve the loss of genes; rather, it is driven by the selective expression and repression of specific genes within each cell type.12

Differentiation is primarily controlled by the regulation of gene expression, which determines which proteins a cell produces. Key mechanisms include:13

• Transcription Factors: These proteins bind to specific regulatory sequences in the DNA to activate or repress the transcription of genes. By working in combination, they dictate a cell's developmental fate.14
• Epigenetic Modifications: Chemical changes, such as DNA methylation and modifications to histones, alter the structure of chromatin. This determines whether DNA is in an "open" configuration accessible to the machinery of transcription or a "closed" state that silences gene activity.13
• Cell Signaling: During biological development, cells receive signals from their environment or neighboring cells—such as growth factors or lateral inhibition signals like the Notch-Delta pathway—which trigger the cascades that lead to specialization.35

Once a cell commits to a specific pathway, these regulatory mechanisms maintain a stable and persistent differentiated state.15