Gene regulation is the process of controlling which genes in a cell’s DNA are expressed.
Various methods of gene regulation and the mechanisms used to control gene expression are epigenetic, transcriptional, post-transcriptional, translational, and post-translational controls in eukaryotic gene expression, and transcriptional control in prokaryotic gene expression.
In prokaryotic cells, the control of gene expression is mostly at the transcriptional level. The transcription regulation is the primary method to control what type and how much of each protein is expressed.
Consequently, in a eukaryotic cell, the processes of transcription and translation are physically separated by the nuclear membranes. Transcription occurs only within the nucleus, and translation occurs only outside the nucleus within the cytoplasm. The regulation of gene expression can occur at all stages of the process. Regulation may occur when:
- the DNA is uncoiled and loosened from nucleosomes to bind transcription factors (epigenetics);
- the RNA is transcribed (transcriptional level);
- the RNA is processed and exported to the cytoplasm after it is transcribed (post-transcriptional level);
- the RNA is translated into protein (translational level); or
- after the protein has been made (post-translational level).
Key Points
• Prokaryotic gene expression is primarily controlled at the level of transcription.
• Eukaryotic gene expression is controlled at the levels of epigenetics, transcription, post-transcription, translation, and post-translation.
• Prokaryotic gene expression (both transcription and translation) occurs within the cytoplasm of a cell due to the lack of a defined nucleus; thus, the DNA is freely located within the cytoplasm.
• Eukaryotic gene expression occurs in both the nucleus (transcription) and cytoplasm (translation).
Key Terms
epigenetics: the study of heritable changes caused by the activation and deactivation of genes without any change in DNA sequence
nucleosome: any of the subunits that repeat in chromatin; a coil of DNA surrounding a histone core
transcriptional level: when RNA is transcribed
post-transcriptional level: when RNA is processed and exported to the cytoplasm after it is transcribed
translational level: when RNA is translated into protein
post-translational level: after the protein has been made