Gene control model

In short, there is a common theme of responding to changes which may serve as a model of positive gene control in procaryotes as well as eucaryotes (133) ... 

We note that this theory would be applicable even if LEAFYs.s. and NEEDLY did not control maleness and femaleness there simply needs to be some kind of divergence of functional role between them via neofunctionalization (cf. Lynch, 2002). Increase in the effectiveness of C-function genes controlled by LEAFY s.s. could easily lead to the loss of the relatively vulnerable NEEDLY, thereby allowing the immediate (and potentially saltational Bateman and DiMichele, 2002) formation of bisexual cones as flower precursors. The Pleiotropy Constraint model helpfully allows co-expression ofboth the male and female programmes in a single determinate meristem in contrast with the Mostly Male theory, there is no requirement for ectopic expression of either the female or the male developmental programmes. 

Caplan, A. I., and Ordahl, C. P., 1978, Irreversible gene repression model for control of development. Science 201 120. 

More than 30 years ago Jacob and Monod introduced the Escherichia coli lac operon as a model for gene regulation. The lac repressor molecule functions as a switch, regulated by inducer molecules, which controls the synthesis of enzymes necessary for E. coli to use lactose as an energy source. In the absence of lactose the repressor binds tightly to the operator DNA preventing the synthesis of these enzymes. Conversely when lactose is present, the repressor dissociates from the operator, allowing transcription of the operon. 

To study the effect of an increased gene dosage of GR, Reichardt et al. (2000) and van den Brandt et al. (2007) generated rodent models of GR overexpression. These approaches confirmed that GR controls neuronal and immune functions in a dosage-dependent manner. These results highlight the importance of tight control of GR expression in target tissues and may explain... 

Histone acetylation is a reversible and covalent modification of histone proteins introduced at the e-amino groups of lysine residues. Histones and DNA form a complex - chromatin - which condenses DNA and controls gene activity. Current models interpret histone acetylation as a means to regulate chromatin activity. 

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