Cell division is the process by which a parent cell divides into two or more duplicate cells. Meiosis and mitosis are the two different types of cell division. Meiosis is a type of sexual production in which the mother cell produces four daughter cells, each with half the number of the parent's genetic information. Mitosis is a type of asexual production that produces two daughter cells genetically identical to the parent cell. Both meiosis and mitosis have stages of cell division, and the stages are; prophase, metaphase, anaphase, and telophase. The main difference between the two is that in mitosis, the cell reproduced is identical to the parent cell, while meiosis creates genetically different cells. Mitosis produces two diploid daughter cells, while meiosis produces four haploid daughter cells.
The duration of meiosis is much longer than mitosis. In mitosis, during prophase one, the cell breaks down into separate entities, the nuclear breaks down, and spindle fibers are formed at the opposite poles at each end. This process is usually shorter taking about 10 hours. In meiosis, the process takes time during prophase 1, which is the first phase. Prophase 1 comprises of another five stages; leptotene, zygotene, pachytene, diplotene, and diakinesis. The five stages take more time (Jaramillo-Lambert et al., 2007). Tetrad formation, which consists of four chromatids made up of homologous chromosomes lined up, occurs in meiosis while it doesn't occur in mitosis.
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The chromosomes' behavior during meiosis generates variation, and this behavior includes recombination or crossing over of homologous chromosomes during prophase 1, the chromosomes each inherited from the parent pair within their lengths in each gene. Breaks occur along the chromosomes, and after they rejoin, they exchange their genes, therefore, creating genes with a unique combination. Independent assortment is another behavior in chromosomes where the chromosomes move without decree or order to separate poles during meiosis. A gamete will end up with 23 chromosomes after meiosis, but an independent assortment will ensure that each gamete will consist of one of the many different combinations of chromosomes.
Mendel’s law of independent assortment states that two alleles of two or more different genes get sorted into gametes independently of one another. The allele a gamete receives for one gene does not affect or influence the allele received by the other gene. Independent assortment only occurs in meiosis. Mendel came up with the law of independent assortment after conducting experiments on peas. He bred two different pea plants with different characteristics, and then he took pea plants with round yellow peas and those that had wrinkled green peas and bred them. The yellow and round were dominant over the wrinkled green ones, so the results of the breeding were peas that were yellow and round. He then bred the first generation, and the result in the peas produced was no longer just yellow and rounded or green and wrinkled. Some were green and rounded, while some were yellow and wrinkled. To be precise, they showed their characteristics in a ratio of 9:3:3:1. Nine became round and yellow, three green and round, the other three wrinkled and yellow, and one was green and wrinkled (Marks, 2008). This proved Mendel's law that each of the peas bred gave their offspring one allele, and since the yellow ones had dominant traits, they masked the green and wrinkled traits in some plants.
References
Jaramillo-Lambert, A., Ellefson, M., Villeneuve, A. M., & Engebrecht, J. (2007). Differential timing of S phases, X chromosome replication, and meiotic prophase in the C. elegans germline. Developmental biology, 308(1), 206-221.
Marks, J. (2008). The construction of Mendel's laws. Evolutionary Anthropology: Issues, News, and Reviews, 17(6), 250-253.
