Sordaria Lab
Effects of Crossing Over in Sordaria fimicola
Abstract
Sexual reproduction in organisms is a cause for genetic variation. This can be seen through the process of meiosis in Sordaria fimicola because of the effects of crossing over and independent assortment that occur in meiosis I. Before performing this experiment we hypothesized that we would be able to see that crossing over did indeed occur in the S. fimicola. We tested our hypothesis by growing our own culture and observing it under a microscope. By counting and recording the types of asci we were able to find that our hypothesis had been correct. This has now led us to know that sexual reproduction causes an increase in genetic variation in organisms such as, Sordaria fimicola.
Introduction
Organisms reproduce in two ways: asexually and sexually. Sexual reproduction can be defined as the reproduction involving the union of gametes or when genetic material from two parents combine to form offspring (Cyr). Offspring produced from sexual reproduction have a unique genetic make-up, which can either be beneficial or destructive to them (Saleem). Close to all known organisms use this kind of reproduction during some moment in their lifetime. If this is true, however, why is not every species seemingly genetically identical? To answer this, one must observe the chromosome behavior during the sexual reproduction life cycle also known as meiosis. Meiosis is the process of cell division in which gametes are produced. It results in four haploid (IN) cells from two diploid (2N) cells (Cyr). In meiosis I, crossing over and independent assortment of the chromosomes occur. These two processes increase the genetic variation within the cell either benefiting or hurting the cell’s ability to adapt (natural selection). After these two events have occurred, the chromosomes will then proceed through all four stages and produce two daughter cells (Cyr). In meiosis II, the two daughter cells each again proceed
Abstract
Sexual reproduction in organisms is a cause for genetic variation. This can be seen through the process of meiosis in Sordaria fimicola because of the effects of crossing over and independent assortment that occur in meiosis I. Before performing this experiment we hypothesized that we would be able to see that crossing over did indeed occur in the S. fimicola. We tested our hypothesis by growing our own culture and observing it under a microscope. By counting and recording the types of asci we were able to find that our hypothesis had been correct. This has now led us to know that sexual reproduction causes an increase in genetic variation in organisms such as, Sordaria fimicola.
Introduction
Organisms reproduce in two ways: asexually and sexually. Sexual reproduction can be defined as the reproduction involving the union of gametes or when genetic material from two parents combine to form offspring (Cyr). Offspring produced from sexual reproduction have a unique genetic make-up, which can either be beneficial or destructive to them (Saleem). Close to all known organisms use this kind of reproduction during some moment in their lifetime. If this is true, however, why is not every species seemingly genetically identical? To answer this, one must observe the chromosome behavior during the sexual reproduction life cycle also known as meiosis. Meiosis is the process of cell division in which gametes are produced. It results in four haploid (IN) cells from two diploid (2N) cells (Cyr). In meiosis I, crossing over and independent assortment of the chromosomes occur. These two processes increase the genetic variation within the cell either benefiting or hurting the cell’s ability to adapt (natural selection). After these two events have occurred, the chromosomes will then proceed through all four stages and produce two daughter cells (Cyr). In meiosis II, the two daughter cells each again proceed
References: Cyr, R. 2002. Heredity and the Life Cycle. In, Biology 110: Basic concepts and biodiverity course website. Department of Biology, The Pennsylvania State University Saleem, Muhammad. 2001. Inherited Differences in Crossing Over and Gene Conversion Frequencies Between Wild Strains of Sordaria fimicola From "Evolution Canyon". University of Haifa, Israel.