Hox genes Encode transcription factors bearing a DNA-binding portion called the homeodomain. Originally identified in Drosophila through the homoeotic effects of their mutation. In vertebrates their expression is strongly associated with the rhombomeric domains of the hindbrain.

Pax genes Encode transcription factors with a DNA-binding domain encoded by a sequence called the "paired box.'' Certain Pax genes are expressed in longitudinal domains within the hindbrain.

raphe Ventral seam of the brain stem, derived from the embryonic floor plate. Contains commissural axons and neuron populations termed the raphe nuclei.

reticular formation Central region of the brain stem extending from mesencephalon to medulla oblongata and containing relatively diffuse populations of neurons. Has a reticular appearance in histological sections stained to reveal nerve fibers. Regulates a wide variety of neural functions.

rhombencephalon Most caudal of the three primary brain vesicles; synonymous with the term "hindbrain." Assumes a form roughly approximating a rhombus during later development and eventually gives rise to the medulla oblongata, pons, and the greater portion of the cerebellar primordium.

rhombic lip Region of the hindbrain rimming the dorsolateral recess of the fourth ventricle.

rhombomeres Rhombencephalic segments, transiently visible as swellings or partitions during early stages of hindbrain development.

Conquering Fear In The 21th Century

Conquering Fear In The 21th Century

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