Transcription factors position RNA polymerase at the transcription startpoint. Collagen Synthesis a. The collagen peptide has a 3' untranslated region. Most of the collagen peptide is spliced out and degraded in the endoplasmic reticulum. Collagen fibers are hollow tubes consisting of globular subunits.
Collagen fibers self-assemble in the extracellular space.
Polar Coordinate Model a. The polar coordinate model assigns positional values to cells in polar coordinates. Intercalary regenerates are always derived from more distal cells. The shortest intercalation rule states that the short axis of a rectangular field is restored before the long axis. The polar coordinate model is based on two morphogens.