Selective expression of genes refers to the phenomenon that genes are selectively expressed under specific spatial and temporal conditions during cell differentiation, resulting in the formation of cells with different morphological structures and physiological functions. Different parts of the genome are expressed at different stages and parts of an organism’s individual development through regulation at the gene level and transcription level, and the result is cell differentiation and individual development. Because mitosis produces daughter cells with the same genetic material, each somatic cell has the same genes, but not every gene in a cell is selectively expressed. When a gene is selectively expressed, the cell is going to produce different proteins, which is called differentiation, and is essentially the selective expression of genes. In addition, gene expression is a complex process that can be selectively expressed by external environmental interference. For example, light, radiation, ultraviolet light, etc. can alter gene expression.