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Neurospora crassa


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The ascomycete fungus upon which many of the classical studies of biochemical genetics were performed. In Neurospora each set of meiotic products is arranged in a linear fashion, and therefore the particular meiotic division at which genetic exchange occurs can be determined by dissecting open the ascus and growing the individual ascospores (see ordered tetrad). The haploid chromosome number of this species is 7, and seven detailed linkage maps are available. Neurospora is estimated to have a genome of 38.6 million nucleotide base pairs. It has around 10,000 genes, but only about 1,400 have counterparts in Drosophila, Caenorhabditis, or humans. More than half of its genes have no similarity to those in the other fungi that have been sequenced (Saccharomyces and Schizosaccharomyces). There are about 1.7 introns per gene, with an average intron size of 134 nucleotides. Neurospora has a lower proportion of genes in multigene families than any other species for which data are available. This is because it has evolved repeat-induced point mutation (RIP) (q.v.), a mechanism for detecting and mutationally inactivating DNA duplications. Dispersed throughout the genome are 424 tRNA genes and 74 5S rRNA genes. There are also 175–200 copies of a tandem repeat that contains the 17S, 5.8S, and the 25S rRNA genes. These are localized in the nucleolus organizer which somehow protects them from RIP. The Neurospora mitochondrial DNA contains 60,000 nucleotide pairs. See Classification, Fungi, Ascomycota; Chronology, 1927, Dodge; 1941, Beadle and Tatum; 1944, Tatum et al.; 1948, Mitchell and Lein; 2003, Galagan et al.; Genome Sizes and Gene Numbers.

Subjects: Genetics and Genomics.


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