In bacteria, gene regulation maintains internal flexibility, turning genes on and off in response to environmental changes. In multicellular eukaryotic organisms, gene regulation brings about cellular differentiation.
A gene may be regulated at a number of points along the pathway of information flow from genotype to phenotype (Figure 16.1). First, regulation may be through the alteration of gene structure. Modifications to DNA or its packaging may influence which sequences are available for transcription or the rate at which sequences are transcribed. DNA methylation and changes in chromatin are two processes that play a pivotal role in gene regulation.
A second point at which a gene can be regulated is at the level of transcription. For the sake of cellular economy, it makes sense to limit protein production early in the transfer of information from DNA to protein, and transcription is an important point of gene regulation in both bacterial and eukaryotic cells. A third potential point of gene regulation is mRNA processing. Eukaryotic mRNA is
Levels of gene control
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