Among the proteins found in cells are enzymes that catalyze biochemical reaction. Enzymes speed up the rate of a reaction that allows life to continue. A simple way to think of the flow of information from DNA to mRNA to protein is the molecular trinity that is central to all life and is known as the central dogma. We may think of humans as individuals who enter the world abruptly and leave the same way. This is not the way it happens however, our genes existed before birth and will exist after our death if we succeed in reproduction.
Cells can arise only from cells that already exist.
They do this by one of life's defining features, reproduction. Parents transmit DNA to their offspring which allows their offspring to look like them. The process starts with a single cell that contains the DNA of one parent in asexual reproduction or two parents in sexual reproduction. After the ovum is fertilized, the single cell divides numerous times and the cells become specialized cells known as tissue and organs, which form complete individual. The instructions for each stage were written into the DNA long before reproduction.