The two H2A.H2B dimers each associate with 30 bp of DNA on either side of the central 60 bp of DNA bound by H3 and H4.

TLS Online TPP Program

#Id: 7407

#Unit 5. Developmental Biology

The segment polarity genes encode proteins that are constituents of the Wnt and Hedgehog signaling pathways.

TLS Online TPP Program

#Id: 7408

#Unit 5. Developmental Biology

The engrailed gene is activated in cells that have high levels of the Even-skipped, Fushi tarazu, or Paired & repressed in cells that have high levels of Odd-skipped, Runt, or Sloppy-paired

TLS Online TPP Program

#Id: 7409

#Unit 5. Developmental Biology

The wingless (wg) gene is activated in those bands of cells that receive little or no Even-skipped or Fushi tarazu protein, but which do contain Sloppy-paired

TLS Online TPP Program

#Id: 7410

#Unit 5. Developmental Biology

Once wingless and engrailed expression patterns are established in adjacent cells, this pattern must be maintained to retain the parasegmental periodicity of the body plan.

TLS Online TPP Program

#Id: 7411

#Unit 5. Developmental Biology

TLS Online TPP Program

#Id: 7412

#Unit 5. Developmental Biology

The maintenance of patterns is regulated by reciprocal interaction between neighboring cells: cells secreting Hedgehog protein activate wingless expression in their neighbors, and the Wingless protein signal, which is received by the cells that secreted Hedgehog, serves to maintain hedgehog (hh) expression