Meiosis is part of the sexual life cycle and occurs in all sexually reproducing organisms. It is a method of cell division that produces gametes.
Of course you remember Gregor Mendel as "that pea guy," well known for his pioneering genetics work with Pisum sativum, the garden pea.
Mendel was a Austrian monk who apparently had a lot of time on his hands. He was the gardener in his monastery which at that time was in Austria, now in Brno in the Czech Republic and noticed that there was some variation in the way the peas looked: He thought that there must be something that was passed on through the generations of peas that dictated the phenotype of the peas, i.
Through a series of very careful experiments, he meticulously crossed peas with different genotypes to see what their offspring looked like. He found that many of the traits seemed to be independent of one another and came up with his Law of Independent Assortment. Mendel also did crosses of true-breeding tall plant with true-breeding short plants.
Mendel found that all of their offspring were tall. Under the Blending theory, the offspring should have all been intermediate in height. When he crossed these tall offspring with one another, he found a 3: Mendel called this the Law of Segregation, that traits would segregate from one another in the second generation.
Mendel thought that there were some segregating "factors" that could account for this phenomenon. We now know that it is the process of meiosis that accounts for these ratios.
Without going into all the gory details, because of the way that meiosis occurs in the ascus, the products of meiosis the tetrad of two pairs of sister chromatids show up in the ascospores in the exact order in which they separated from one another. This phenomenon is largely due to the narrow cylindrical shape of the ascus, which forces the meiotic spindle to line up parallel to the long axis of the ascus.
In all three of these species, the meiotic division is followed by one mitotic division, resulting in eight spores per ascus. The utility of Sordaria in genetics stems from its very strict method of sexual reproduction.
It is a member of the Ascomycota, which means that it bears its sexual meiotic ascospores in a sac called an ascus. In turn, the asci are borne in a special fruiting structure called a perithecium.
All of the asci in one perithecium are more or less conected at their bases, forming a layer of cylinders kind of squished into the perithecium.
The perithecium is flask-shaped, which means that it is basically ovoid, but elongated at one end. See the picture to the right, where the perithecia are shown growing on agar plates.
The lighter brown dots are immature perithecia.
The elongated tip of the perithecium is actually hollow; the hole is called the ostiole. The ostiole allows the ascospores to be discharged into the outside world in an interesting way: As the ascus reaches the outside, the ascospores are forcibly discharged via water pressure from within the fruiting body.
The spent ascus withers, and a new one grows into the ostiole to take its place. If there is not enough water, the perithecium can dry out and revive to shoot out its spores later. Thus the ascospores can be discharged over a very long period of time, kind of a timed release of spores.
To the left you can see an animation of ascospore production from Jim Worrall at ForestPathology. Go there now to learn more! In the example at the top of this page, you can see three perithecia that have been crushed to release the intact asci all at once.
The perithecium on the left is from a self-cross of a mycelium whose DNA coded for dark ascospores. The perithecium on the right was formed by a self-cross of a mycelium whose DNA coded for tan ascospores.
The perithecium in the center was formed when the two types of mycelia crossed with one another. You can clearly see the asci that have ascospores of two colors. There are two different patterns-- 4: However, unlike those four, Sordaria fimicola does not bear its perithecia in or on a stroma, a structure composed of sterile hyphae, but rather bears its perithecia singly on the substrate.
This provides less protection for the perithecium, but allow more flexibility in timing of the fruiting for maximum spore discharge.Sordaria fimicola is an ascomycete fungus that normally grows on decaying organic material.
It may also be frequently found in introductory laboratory settings where it is manipulated and examined for educational purposes. Meiosis and Genetic Diversity in Sordaria Biology Lab Introduction: In Israel there exists multiple spots in the mountains called Evolution Canyons, which are all located between a southern facing slope (SFS) and a northern facing slope (NFS).
Meiosis and Genetic Diversity in Sordaria INTRODUCTION Sordaria fimicola is an ascomecyete fungus studied for its product of meiosis and mitosis that form 8 haploid spores. These spores are contained in a fruiting body called perithecia.
Volpe 1 Audra Volpe Fengping Dong Bio Lab Section 46 13 October Meiosis and Genetic Diversity in Sordaria (Lab Homework #4) Directions: The goal of this assignment is to understand the role of meiosis, recombination, and mitosis in the life cycle and genetic diversity of the model organism Sordaria fimicola%(39).
Meiosis (/ m aɪ ˈ oʊ s ɪ s / (); from Greek μείωσις, meiosis, which means lessening) is a specialized type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell that gave rise to them.
This process occurs in all sexually reproducing single-celled and multicellular eukaryotes, including animals, plants.
Meiosis (/ m aɪ ˈ oʊ s ɪ s / (); from Greek μείωσις, meiosis, which means lessening) is a specialized type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell that gave rise to them. This process occurs in all sexually reproducing single-celled and multicellular eukaryotes, including animals, plants.