Meiosis Essay

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Meiosis is a type of cell division required for sexual reproduction and produces gametes or spores. During Meiosis I, DNA replication occurs and chromosomes line up on the equator as a homologous pair known as chromatids. At the first stage of Meiosis, Prophase I, DNA of individual chromosomes coils more and more tightly, known as DNA condensation. Sister chromatids then attach to specific sites on the nuclear envelope to bring the homologous pair of chromosomes close together. The sister chromatids line up so they can pair up with its corresponding "sister gene" on the homologous chromosome. Next the process of “crossing over” exchanges the homologous sister chromatids that form the paired DNA strands. This involves the separation of the DNA double helix in one paternal and one maternal chromatid and joining of the respective ends. At the end of meiosis I, each chromosome is still composed of two chromatids held together by a particular DNA sequence called the centromere. Gregor Mendel came up with two laws following his experiment on pea plants. The first law is called “The Law of Segregation” is when two coexisting alleles of an individual for each trait segregate during gamete formation so that each gamete gets only one of the two alleles. Alleles again unite at random fertilization of gametes. Mendel’s Pea Experiment showed that a cross between a green pod plant and a yellow pod plant produced only green pod plants for the F1 generation. It appeared that the yellow pod characteristic had disappeared. However, the F2 generation threw up an unexpected result; the yellow pod variant appeared in a quarter of this generation which proved his law correct. The second law is called “The Law of Independent Assortment”. This occurs in Meiosis I in eukaryotic organisms in the anaphase stage and produces a gamete with an assortment of the organism's

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