|MoBio||Overview of Gene Expression||Chapter 4|
An organism may contain many types of somatic cells, each with distinct shape and function. However, they all have the same genome. The genes in a genome do not have any effect on cellular functions until they are expressed. Different types of cells express different sets of genes, thereby exhibiting various shapes and functions.
Gene expression means the production of a protein or a functional RNA from its gene. Several steps are required:
For RNA genes (tRNA and rRNA), the expression is complete after a functional tRNA or rRNA is generated. However, protein genes require additional steps:
The central dogma
According to the above process, the flow of genetic information is in the following direction:
This rule was dubbed the central dogma, because it was thought that the same principle would apply to all organisms. However, we now know that for RNA viruses, the flow of genetic information starts from RNA.