How do genes create organisms?
Genes are not always active. Sometimes they are busy churning out their encoded protein or RNA, sometimes they are shut off completely. And their activity can be tuned at different levels. During the development of a complex organism from a single cell, thousands of genes flash on and off in complicated patterns. One of the most important jobs genes have is to create proteins called transcription factors, which coordinate the activities of other genes. As an eye or a finger is created, for example, transcription factors ensure that a characteristic series of genes get activated in surrounding tissue to build that structure. Proteins and structures they create can also serve many other functions: generating energy, creating new molecules or serving directly as the brick and mortar of structures like muscle. Genes also shape organisms by driving the replication, movement, activity and death of cells.
