Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Stem cell behavior proposed in invertebrate model systems. (A) Three possible cell division strategies: invariant asymmetric division (left); invariant symmetric division (middle); combination of asymmetric and symmetric divisions (right). (B) Cell-extrinsic (upper) and -intrinsic (lower) regulation of asymmetric cell division. (C) Two possible stem cell behaviors to replenish a new stem cell: symmetric division (upper) and dedifferentiation (lower).
