the development and differentiation of an embryo into a mature organism are the results of the coordinated regulation of expression of several sets of genes . While somatic cells in an organism generally share the same genome, it is the differential expression of these genes—turning specific genes on or off in a precise sequence—that allows cells to specialise into distinct tissues and organs . This process, alongside growth, constitutes the broader biological phase of development . Mastering these regulatory concepts is a high-priority strategy for medical aspirants, as NCERT textbooks provide the foundation for approximately 95% of NEET Biology questions .