Auxotrophic markers and the cytogenetics of Filobasidiella neoformans.

In the sexual phase of Cryptococcus neoformans four post-meiotic nuclei give rise to the nuclei of four long chains of basidiospores. If there is fixed relationship between one post-meiotic nucleus and one chain the result should be genetic homogeneity within single chains; random composition of chains would represent the opposite case. We tested for homogeneity in single chains from crosses of niacin-auxotrophs to the wild type by dissecting single chains of basidiospores from mature fruiting bodies. Out of 14 chains, 11 were homogeneous; the probability of obtaining this result by random processes was less than 0.01. These results suggest that mitotic products of a particular post-meiotic nucleus may be channeled into a particular basidiospore chain.