ECENT studies of the highly differentiated pachytene chromosomes of R the tomato have indicated that this plant can be used in the analysis of chromosome structure in relation to chromosome behavior and gene location (BROWN 1949; BARTON 1950). In general, the twelve paired chromosomes of the tomato pachytene complement are differentiated into densely staining (chromatic) regions proximally on e...

In plants, small non-coding RNAs (≈20-30 nt) play a major role in a gene regulation mechanism that controls development, maintains heterochromatin and defends against viruses. However, their possible role in cell division (mitosis and meiosis) still remains to be ascertained. ARGONAUTE (AGO) proteins are key players in the different small RNA (sRNA) pathways. Arabidopsis contains 10 AGO protein...

qWO previous studies have provided extensive tetrad data on crossing-over in the centromere region of linkage group I. LINDEGREN and LINDEGREN (1942) found an excess of multiple exchanges across the centromere. These multiple exchanges included a proportion of %strand pairs in excess of the 0.25 expected if all four chromatids participated in exchanges at random. Such a deviation might be attri...

NTIL comparatively recently there has been no compelling evidence U that genetic “interference” involves more than the occurrence of one crossover reducing the chance of another occurring in nearby regions. Genetic data from Drosophila have generally been interpreted as indicating that there is no “chromatid interference,” that is, that a crossover between two of the four chromatids does not in...