Why does only a part of the genes “work” in the various cells of an organism?

In various cells of an organism, only part of the genes “works”, because each cell needs to synthesize different proteins, depending on the functions performed by a particular cell.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.