Notes On Osmosis And Diffusion

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Title: Osmosis and Diffusion Introduction There are two types of nuclear division, mitosis and meiosis. Mitosis is usually used for the growth and replacement of somatic cells, while meiosis produces the gametes or spores used in an organism’s reproduction. Mitosis is the first of these studied in this lab. It is easily observed in cells that are growing at a rapid pace such as whitefish blastula or onion root tips, which are used in this lab. The root tips contain an area called the apical meristem that has the highest percentage of cells undergoing mitosis. The whitefish blastula is formed directly after the egg is fertilized. This is a period of rapid growth and numerous cellular divisions where mitosis can be observed. Just before…show more content…
This is where crossing over occurs resulting in the recombination of genes. Metaphase I moves the tetrads to the metaphase plate in the middle of the cell, and Anaphase I reduces the tetrads to their original two stranded form and moves them to opposite poles. Telophase I then prepares the cell for its second division. Meiosis II generally resembles mitosis except that the daughter cells are haploid instead of diploid. DNA replication does not occur in Interphase II, and prophase, metaphase, anaphase, and telophase occur as usual. The only change is the number of chromosomes. The process of crossing over can be easily studied in Sordaria fimicola, an ascomycete fungus. Sordaria form a set of eight ascospores called an ascus. They are contained in a perithecium until they are mature and ready for release. Crossing over can be observed in the arrangement and color of these asci. If an ascus has four tan ascospores in a row and four black ascospores in a row (4:4 arrangement), then no crossing over had taken place. However, if the asci has black and tan ascospores in sets of two (2:2:2:2 arrangement) or two pairs of black ascospores and four tan ascospores in the middle (2:4:2 arrangement), then crossing over had taken place. Hypothesis Mitosis occurs in whitefish blastula and onion root tip, and it is easily observable. Meiosis and crossing over occurs in the production of gametes and spores. Materials This lab

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