Segregation of homologous chromosomes during meiosis I depends on appropriately positioned crossovers/chiasmata. Crossover assurance ensures at least one crossover per homolog pair, while interference reduces double crossovers. Here, we have investigated the interplay between chromosome axis morphogenesis and non-random crossover placement. We demonstrate that chromosome axes are structurally m...

Although recombination is essential to the successful completion of human meiosis, it remains unclear how tightly the process is regulated and over what scale. To assess the nature and stringency of constraints on human recombination, we examined crossover patterns in transmissions to viable, non-trisomic offspring, using dense genotyping data collected in a large set of pedigrees. Our analysis...

Haidinger brushes, an entoptic phenomenon perceived only through the most central macular retina, have been used in addition to kinetic and static perimetry with the Tubingen perimeter for determining macular sparing and splitting in hemianopic patients. Seven patients were examined: 2 with a bitemporal hemianopia resulting from traumatic damage to the optic chiasma, and 5 with a homonymous hem...

This study used in vitro brainstem-spinal cord preparations from the American bullfrog, Rana catesbeiana, to examine the influence of central descending inputs on breathing pattern formation. In preparations with an episodic pattern of fictive breathing, a transection slightly caudal to the optic chiasma produced a continuous breathing pattern and increased the overall frequency of fictive brea...

is some evidence from studies of related species of plants that low T E a E a frequency is associated with outcrossing and high chiasma frequency is associated with selfing (reviews in GRANT 1958; BODMER and PARSONS 1962). From this it has been inferred that crossover rates have been adjusted by natural selection toward high values in selfing species to compensate for the restrictions imposed o...

The extent, and the development, of the ipsilateral retinothalamic projection in the frog Xenopus laevis have been studied using terminal degeneration and autoradiographic techniques. This ipsilateral projection derives only from those retinal areas receiving visual information from the binocular portion of the visual field. In Xenopus, the ipsilateral retinothalamic projection arises from a la...