Gene expression and its control
What makes a cell act and look a certain way? Why do two cells express different phenotypes? When talking about two different individuals, one might start by highlighting differences between the complements of genes present in each. In bacteria, such differences are very pronounced. The presence of mobile DNA elements, with ‘plug-and-play’ attributes, seemingly randomly scattered amongst members of a population provide phenotypic variation to the population as a whole (Avison and Bennett, 2005). Smaller genetic variation, caused by point mutations, deletions and duplications are found in populations of bacteria and eukaryotic organisms alike. Mutations within coding sequences can alter, or even destroy the activity of the protein produced, and many examples of phenotypic variation caused by such mutations are known in our own species. Most help give us a wonderfully varied society; some cause terrible genetic disease (Avison and Bennett, 2005; Crow, 2000).