Answer:
Differential gene expression is possible even though all somatic cells carry identical genes and genome due to epigenetic modifications and cellular differentiation.
Epigenetic modifications refer to chemical changes that occur on DNA or histone proteins, which can alter gene expression without changing the DNA sequence itself. These modifications include DNA methylation, histone acetylation, and chromatin remodeling. Depending on the specific epigenetic modifications present, different genes can be turned on or off in different cells, leading to differential gene expression.
Cellular differentiation is also a key factor in differential gene expression. During development, cells become specialized and take on distinct functions. This specialization is due to changes in gene expression patterns that result in cells with unique phenotypes. For example, muscle cells express different genes than liver cells, leading to differences in structure and function.
In summary, while somatic cells carry identical genes and genome, differential gene expression is possible due to epigenetic modifications and cellular differentiation. These mechanisms allow for the development of specialized cells and complex organisms.