Evolutionary biology. Twinned genes live life in the fast lane

On page 1151, researchers describe new insights into how genes arise and fuel evolution. By trolling through sequence data for nine very distinct organisms, they have uncovered evidence that genes are copied far more frequently--and the duplicates are lost from the genome far faster--than researchers had thought. What's more, the work suggests that some duplicate genes play a key role in the evolution of new traits and in speciation.     

Synaptic vesicles in electron micrographs of freeze-etched nerve terminals

Freeze-etched neuropil of the cat subfornical organ was examined with the electron microscope for synaptic vesicles. Round vesicles were found exclusively in both unfixed and aldehyde-fixed specimens. Range of diameters and histograms failed to differ significantly between freeze-etched and conventionally prepared material. The mnode of distribution of diameters was approximately 500 angstroms. Round stomata (approximately 350 angstromns in diameter) were found at the outer surface of the plasmalemma of nerve terminials; they are interpreted as pinocytotic vesicles.     

Synaptic vesicles of inhibitory and excitatory TERMINALS IN THE CEREBELLUM

Populations of synaptic vesicles within cerebellar terminals considered excitatory or inhibitory on the basis of physiological evidence differ with respect to size and shape. Size rather than shape appears to be the main morphological difference between these populations. Elongation of vesicles is depenident on fixation with aldehyde fixatives, and both size and elongation change with age mainly during maturation.