Article Abstract:
A general pattern for the interpretation of positional information of the structures in an organism and the regulation of cellular behavior is described. The steps involved in the link between patterning information and morphogenesis are the interpretation of complex patterning information by a regulatory factor, the transduction of a signal produced by this factor and the regulation of specific cell biological processes in response to this transduction. In some instances, a single factor completes the link between patterning information and cell behavior, while in others, distinct factors undertake individual steps, thus making the link between patterning and cell behavior more complex.
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Article Abstract:
The cells in the G2 phase are unable to replicate because their nuclear membranes do not contain the licensing factor and replication starts after the nuclear envelope breaks during mitosis. Experiments show that the minichromosome maintenance genes are required for the replication process to start in the G2 nuclei. Complexes of cyclin-dependent kinase and cyclin are present in the S and the G2 phase and prevent replication. However, according to the kinase model a collapse in the nuclear kinase activity is required for the initiation of replication.
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Article Abstract:
Proteolysis and degradation of cyclin appears to be required for exit from mitosis and return to interphase. In Drosophila, however, only a small amount of cyclin destruction may occur since total cyclin levels do not oscillate. Cdk1 activity is indicated by antibody detection of histone H3 phosphorylation. Cdk1 inactivation occurs close to the spindle poles in syncytial embryos. Syncytial cycles may have modified mechanisms for exit from mitosis.
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