Retinotectal fibres from different parts of the retina have been filled with Horse Radish Peroxidase (HRP). During their course down the nerve their ordering decays, but it is re-established at the chiasma, except for nasal fibres which remain relatively disordered. The consequences of this for development are discussed.

According to the model of FOSS, LANDE, STAHL and STEINBERG, chiasma interference is a reflection of the requirement for crossovers to be separated by an organism-specific number of potential conversion events without associated crossovers. This model predicts that tetrads with close double crossovers should be enriched for conversion events that themselves are not associated with crossing over....

Purpose: The aim of this study is to determine and define differential magnetic resonance imaging (MRI) findings pituitary adenomas craniopharyngiomas. Materials methods: This retrospective analysis was performed on MR 45 41 craniopharyngiomas with solid cystic mixed appearance. MRI including shape ovoid, snowman, lobulation, chiasma compression, cavernous sinus invasion, 3rd ventricle calcific...

CONXENTS LIFE CYCLES ......................................................... 151 RECOMBINATION ....................................................... 152 Tetrad and random spore analysis; procedures ............................ 152 Chromosome maps ................................................... 153 Interference, chiasma, and chromatid .................................... 153 Gene convers...