Term of Award

Spring 2003

Degree Name

Master of Science in Biology

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Department

Department of Biology

Committee Chair

Sara Neville Bennett

Committee Member 1

Wayne A. Krissinger

Committee Member 2

Don Drapalik

Abstract

Following ultraviolet irradiation M-134, a crisp mutant strain and two conidial-shed mutants, E-l and K-44, of Neurospora crassa, were isolated in the Georgia Southern University Neurospora Laboratory. Using scanning electron microscopy differences in morphology among M-134 and other crisp mutants, cr-1, cr-2, cr-3, cr-4, cr-5, and wild type N. crassa were compared. The SEM study revealed that M-134 and the other five crisp mutants all exhibit a reduced mycelial mat and clumps of conidia leading to their crisp-like morphology. Previous preliminary mapping of M-134 indicated that the mutant is in Linkage Group 1 and linked to lys -4 by 9% recombination. The present study also mapped M-134 to the right of lys-4 in Linkage Group 1 with the gene order cys-9 M-134 im-1 displaying 15.4% recombination between M-134 and cys-9 and 5.7% recombination between M-134 and un-1 thus should be designated cr-6.

When E-l and K-44 were compared to the wild type strain, these mutants failed to shed conidia when the culture tubes were inverted and sharply tapped (the tap test), whereas the conidia of wild type produced a visible cloud. Previous SEM indicated that E-l and K-44 conidia stayed in proconidial chains. The present SEM study includes an examination of E-l and K-44, and a comparison between the mutants and csp-1 and csp-2 using wild type as the control. All four of these mutants examined showed conidia staying in proconidial chain whereas the wild type conidia separate from the chains.

Earlier work had shown that crosses of K-44 and E-l to wild type exhibited 1:1 segregation, indicating single genes following Mendelian inheritance. However, no attempts to map the mutants had been made. To begin mapping, K-44 and E-l were crossed to the alcoy tester strain which facilitates mapping mutants to Linkage groups I-VI. Failure to show linkage of either mutant to the six tested linkage groups assumes that both mutants were in the seventh linkage group (LG VII). Since no linkage was found in LG I-VI, both mutants were then crossed to csp-2, located in LG VII to determine allelism and linkage to the mutant. Both crosses produced wild type progeny, ruling out allelism of E-l and K-44 to csp-2. E-l displayed linkage to csp-2 with 37.6% recombination and should be designated csp-3. K-44 showed no linkage to csp-2 and was therefore crossed to mc-3 located in a different part of LG VII also resulting in no linkage.

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