Genetic Evidence of Unusual Meiosis in the Dinoflagellate CRYPTHECODINIUM COHNII

Abstract

Genetic analysis of the homothallic dinoflagellate, Crypthecodinium cohnii, using 16 nonallelic motility mutants, revealed (1) virtual absence of second division segregation and (2) independent assortment of all genes except for: (a) three cases of cross specific, "false" linkage and (b) one possible case of linkage with a high percentage of crossing over. The probability that at least two of the 16 genes studied are on one of the approximately 50 (minimal) chromosomes is extremely high and, since recombination is observed between all pairs of markers, it is highly probable that some results from crossing over. This likelihood plus the observed absence of second division segregation and the significant number of two-celled zygotic cysts support the view that the "meiosis" of C. cohnii is a one-division process.