Cell cycle and experimental pattern duplication in the chick wing during embryonic development.

Transient stimulation of cell division within chick wingbud mesenchyme is associated with the reorganization of limb pattern that follows insertion of a small graft from the posterior zone of limb polarizing activity into the anterior border of a host bud. This increase is initiated as an enhanced rate of entry to S phase, correlated with a decrease in packing density among mesenchyme cells, through much of the limb rudiment a few hours after the operations.