<P> A large number of studied regulatory systems come from developmental biology . Examples include: </P> <Ul> <Li> The colinearity of the Hox gene cluster with their nested antero - posterior patterning </Li> <Li> Pattern generation of the hand (digits - interdigits): the gradient of sonic hedgehog (secreted inducing factor) from the zone of polarizing activity in the limb, which creates a gradient of active Gli3, which activates Gremlin, which inhibits BMPs also secreted in the limb, results in the formation of an alternating pattern of activity as a result of this reaction - diffusion system . </Li> <Li> Somitogenesis is the creation of segments (somites) from a uniform tissue (Pre-somitic Mesoderm). They are formed sequentially from anterior to posterior . This is achieved in amniotes possibly by means of two opposing gradients, Retinoic acid in the anterior (wavefront) and Wnt and Fgf in the posterior, coupled to an oscillating pattern (segmentation clock) composed of FGF + Notch and Wnt in antiphase . </Li> <Li> Sex determination in the soma of a Drosophila requires the sensing of the ratio of autosomal genes to sex chromosome - encoded genes, which results in the production of sexless splicing factor in females, resulting in the female isoform of doublesex . </Li> </Ul> <Li> The colinearity of the Hox gene cluster with their nested antero - posterior patterning </Li> <Li> Pattern generation of the hand (digits - interdigits): the gradient of sonic hedgehog (secreted inducing factor) from the zone of polarizing activity in the limb, which creates a gradient of active Gli3, which activates Gremlin, which inhibits BMPs also secreted in the limb, results in the formation of an alternating pattern of activity as a result of this reaction - diffusion system . </Li>

Explain why it is to a cells advantage to have some of its genes under regulation