Sordaria Fimicola

Sordaria fimicola is a microscopic fungal species that produces ordered tetrads. It is commonly used in classrooms because it lacks conidiospores, has a short generation time with matching genotype and phenotype, has known color genes that permit tetrad analysis, easily observable crossing over effects, and does not undergo spindle overlap. In S. fimicola, meiosis occurs in the ascus. The fungus is a haploid organism for the majority of its life. It only becomes diploid when mycelia of two unlike strains fuse. Mycelia are a network of long hyphae filaments which the fungus uses to form sex organs. The newly formed, diploid nucleus must go through mitosis to become haploid again. This will produce eight haploid ascospores held in the ascus.

If the parent alleles do not rearrange until the second division of meiosis, it is called second division segregation of alleles. Gene mapping is the relationship between the frequency of second division segregation and distance (map units) between the genes involved. Recombinant ascospores have chromosomes that were altered by the crossover in metaphase of meiosis. They phenotypically do not represent the parental chromosomes. When spores resemble the parental chromosomes, they are called non-recombinants and they result from being unaffected by the crossover. Tetrad analysis can be used to determine the distance between two genes. When there are tetratypes in the data, one must use this equation (1/2T+NPD)/(Total Tetrads) x100 to find map distance. If there is no tetratypes in the data, then one must use map units=(recombinant spores)/(Total spores(recomb+non-recomb)) x100. These equations will specify the genetic location of genes on a chromosome and their distances apart from one another. The null hypothesis of this experiment is that the ascospores color gene assorts independently and that the phenotype of Grey and Tan are unlinked. The alternative hypothesis is that the Grey and Tan color genes are linked. (Glase,