Gene expression is regulated by several mechanisms, such as posttranscriptional modifications, which are changes that occur after RNA has been transcribed. In eukaryotes, the most common of these posttranscriptional modifications is alternative splicing, in which various final mRNA transcripts are created by splicing together different combinations of exons transcribed from the same gene product. In this way, one gene from a cell can generate numerous messages. Prokaryote mRNA does not undergo posttranscriptional modifications, in fact, transcription and translation occur simultaneously. Genes are also under combinatorial control, which is control by groups of regulatory proteins that work together. Often, only one regulatory protein is required to initiate or halt transcription. These switches control differentiation, the process by which stem cells become specialized cells. These specialized cells can go on to divide, making more cells that share the original cell's specialization. This shared specialization following cell division is done via cell memory, in which the proteins that trigger specialization continue to exist in progeny cells. The passage of this heritable information from parent cell to progeny without changes to the genome is epigenetic inheritance.
At A Glance
Gene expression is controlled after transcription primarily through alternative splicing of the gene after the 5′ cap and 3′ poly-A tail have been added.
Cell differentiation, the process by which a cell is changed from a stem cell to a specialized cell, is controlled by relatively few regulatory proteins working in groups, called combinatorial control.
Cell memory is the process by which all progeny of a parent cell retain the specialization of that cell; DNA methylation is a marker for epigenetic inheritance.
Epigenetic inheritance is a heritable process that includes the passage of genetic information from parent to daughter cell, without alteration to the genome itself.