Meiosis i crossing over an important feature of

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Meiosis I: Crossing OverAn important feature of meiosis is the process called crossing over.Crossing over is responsible for generating much of the diversity that exists within a species. Remember that diversity in a species is one of the hallmark characteristics of living organisms. Infuture modules, you will see that this diversity allows species to survive in changing environmental conditions. So, crossing over is another process that brings variability in the offspring.
Crossing overis a process in which genes swap positions on matching chromosomes. The result is a new combination of genes on each chromosome.By University of Maryland University CollegeCC-BY-NCDuring metaphase I, homologouspairs of chromosomes line up on the metaphase plate. This is very different from mitosis, when sisterchromatids line up, completely independent of their homologues.During anaphase I, homologouspairs are pulled apart, and they move toward the poles of the cell.In telophase I, cytokinesisoccurs and two new daughter cells are formed. Meiosis Iends with the production of two haploiddaughter cells because the homologouspairs of chromosomes have been separated.
Meiosis IIList the stages of meiosis and describe what happens at each stage.Describe the function of meiosis as it relates to sexual reproduction.Predict the number of genes/gene pairs of the progeny cells based on the number of genes of the parental cell.Meiosis IIbegins with two haploid cells, each containing too muchDNA. Remember that while homologouspairs of chromosomeswereseparated in Meiosis I, each homologous chromosome is still connected to its sister chromatid. The presence of a sister chromatidfor each chromosome at the start of Meiosis IImeans that each cell contains too much DNA. The events in meiosis II are almost identical to the events of mitosis.
In Meiosis II(which is essentially like mitosis), the sister chromatids separate from each other. Thus, as the result of meiosis,four haploid cells are produced. Note that those four cells are not always viable. In humans, male germ cells will produce four viable sperm cells. However, in the case of females, only one of the four will survive as an egg.The end result of meiosis is four unique haploid daughter cells. Genetic variability is introduced in various ways during meiosis:1.Crossing over during prophase 1: crossing over introduces novel combinations of traits among offspring.
2.Segregation of chromosomes into gametes: the maternal and the paternal copy of each chromosome pair will segregate to different gametes. However, which goes to which cell is a random process. Thus, the possible number of combinations is astounding: in the case of humans, with 23 chromosomes, it is 223(8,388,608).

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