Signal initiating DNA synthesis

Returning to our speculations on the coordination of biochemical events in mononucleate interspecific somatic hybrids, we would like to go one step further and suggest that the synchronization of the two parental cell cycles to produce a single new cycle is in part the consequence of the attachment of (some or all ) chromosomes of both species to the single nuclear membrane and hence of their simultaneous response to the reaction of the nuclear membrane to the signal initiating DNA synthesis. 

This confiict can be resolved also by assuming that the signal initiating DNA synthesis originates in one or a few chromosomes of the complement and that it travels slowly through the cytoplasm. Such a hypothesis would also explain why a degree of asynchrony between chromosomes similar to that described by Stubblefield is not observed when all chromosomes are located within the same nucleus (rather than in different karyomeres). It becomes, in fact, very attractive when taken in conjunction with the possible role of the attachment of the chromosomes to the nuclear membrane (considered in Section IV, C). 

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