Cytogenetic Studies of Neurospora crassa

Citation

Singleton, Jesse Robertson (1948) Cytogenetic Studies of Neurospora crassa. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/SK7K-FX44. https://resolver.caltech.edu/CaltechETD:etd-08042006-130929

Abstract

The literature pertinent to the nuclear cycle in the life history of Neurospora is reviewed. A description of methods used in the cytological studies is presented, and the most useful are summarized as schedules of treatment. The morphology of the mitotic and pachytene chromosomes of N. crassa is described and diagrammed. The chromosome cycle in the developing ascus is described in detail, and special points of interest are discussed. The cytological basis of spore abortion caused by the presence in the ascus, in the homozygous condition, of genes from the Abbott strains is discussed briefly. Five translocations, three previously found by McClintock (1945) and two others found by the writer, are described and tentatively identified as to the chromosomes involved. From a consideration of the consequences of crossing-over and disjunction in the translocation heterozygote, equations are derived by means of which the frequencies of the various types of exchange and disjunction can be calculated or estimated. Non-random segregation in T4637 following an effective exchange in a single interstitial segment is described, and a possible mechanism suggested.

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