Yeasts sexual reproduction

Yeasts belonging to Basidior cetes form external spores. ia.yiscomjcetes sexual reproduction occurs with the formation of spores in a cell that serves as a spore sac or ascus. Generally four, but sometimes eight or more, spores are formed in each ascus. This is sometimes reflected in the species name, ie,... 

The consequences of histone HI elimination in Tetrahymena and in the three species of fungi are consistent with the interpretation that linker histones do not have a role which is essential for the normal life-cycle of these organisms including sexual reproduction. Indeed, it has been reported that in yeast the HI occurs with a stoichiometry of about one molecule per 37 nucleosomes showing a preferential association with rDNA sequences [126]. The analyses of the effects of HI loss on transcription, particularly in Tetrahymena and yeast, provide strong... 

C c lasmic inheritance transfer of genetic information in eukaryotic sexual reproduction, which is not carried by the chromosomes of the nucleus. C.i. is due to extrachromosomal genetic carriers, e.g. mitochrondrial and plastid DNA. C. i. does not obey Mendelian rules, and it permits mixing of cytoplasmic genetic factors during mitosis. Certain petite mutations of yeast, the killer property of certain strains of Paramecium and leaf pigmentation in Antirrhinum majus are examples of properties transmitted by Ci. 

Sexual reproduction is associated with many yeasts and moulds. A stage in which spores are formed is always involved in the sexual process. Depending on the type of sexual spore formation four groups of moulds can be distinguished Ascomycetes, Basidiomycetes, Zygomycetes, and Oomycetes. The spores are called ascospores, basidiospores, zygospores, and oospores, respectively. 

Fungi are used extensively as model developmental systems in biochemistry and genetics. An early classical study of steroid-mediated morphogenesis involved the Oomycete Ac/i/ya ambisexualis (Raper 1939, 1940). The ascomycetous yeast Saccharomyces cerevisiae is the most extensively studied eukaryote in many areas of signal transduction (Kurjan 1993 Ferguson et al. 1994 Grishin et al. 1994 Schultz et al. 1995), especially as it relates to cell division and sexual reproduction. 

FIGURE 3.3 Life cycle of yeast (1) Asejcual reproduction (budding) with two different diploid mating types (a and a) (2) Sexual reproduction (conjugation) (3) Production of haploid spores by meiosis. 

Ascospores The sexual spore that many yeasts can produce as a mean of reproduction. 

Fig. 1.14. Reproduction cycle of a heterothallic yeast strain (a, a spore sexual signs)...

---