Biology: Sordaria Fimicola

Introduction: The process of Meiosis involves 2 nuclear divisions that result in the formation of four haploid cells (2). Meiosis I is preceded by interphase, during which DNA synthesis occurs and each chromosome is made of two chromatids joined at the centromeres. In meiosis I, chromatids of homologous chromosomes may exchange parts by crossing over. During Prophase I homologous chromosomes come together and synapse. A tetrad consisting of four chromatids is also formed (2). In Metaphase I, the crossed over tetrads line up in the center of the cell, and in Anaphase I, the homologous chromosomes separate and move to opposite ends of the cell. In Telophase I, centriole duplication is completed and cytokinesis and results in 2 haploid cells with replicated chromosomes (2). Before Meiosis II, interphase II takes place and no DNA replication occurs. Meiosis II, a second mitotic cell division then takes place (2). In Prophase II, replicated centrioles separate and move to opposite sides of the chromosome groups. During Metaphase II, chromosomes are centered in the middle of each daughter cell. In anaphase II the centromere regions of the chromatids are separated. Lastly, in Telophase II, the chromosomes are at opposite ends of the cell, a nuclear envelope forms, and sister chromatids are separated resulting in four haploid cells (2). …..Sordaria fimicola is fungus that may be used to show the results of crossing over during meiosis. Sordaria throughout most of its life is haploid, but becomes diploid after the fusion of two different types of nuclei, which forms a diploid nucleus (3). In Sordaria meiosis results in the making of eight haploid ascospores found in a sac called an ascus (1). Most asci are found in a perithecium. The life cycle of Sordaria fimicola begins as a spore is discharged through an ascus. The ascospore then

References: 1. Benson, Jennifer. Lab: Meiosis in Sordaria Fimicola. 28 October 2008. 2. Biology 8th Edition. Campbell, Neil A. and Jane B. Reece. Prentice Hall, c2005.ISBN 0805367772. Pearson Education 800.848.9500. 3. Bio 325 Genetics Lab: Tetrad analysis in Sordaria fimicola. 30 October 2008 4. Mitosis and Meiosis Lab. 31 October 2008