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Concerning Meiosis and Sexual Reproduction, Meiosis I is the first cell division in Meiosis. Meiosis II is the second cell division in Meiosis. These are both part of the overall process of "reduction division" or Meiosis. Meiosis is the division of a germ cell. It involves two fissions of the nucleus. This produces four sex cells (gametes). Each of these sex cells has half the number of chromosomes that the "original" cell had. Therefore, the meaning of the term "reduction division."
Both Meiosis I and Meiosis II include Prophase, Metaphase, Anaphase, as well as Telophase.
In Meiosis I (but not Meiosis II), members of homologous chromosome pairs undergo separation. This results in the separation of genes into the two gametes. The separation of any one pair of chromosomes is independent of any other pair. Meiosis I starts with the contraction or condensation of the chromosomes in the nucleus of the diploid cell. It also begins with the vesiculation or blistering of the nuclear membrane.
Meiosis II is very like Mitosis. Meiosis II is more like Mitosis than it is like Meiosis I. Mitosis is a process of cell reproduction (cell duplication). During this particular process, one cell engenders two genetically identical daughter cells. Mitosis supplies new cells for growth and for the replacement of degraded cells.
In Meiosis II and Mitosis, chromosomes line up; sister chromatids are separated by the action of the spindle fibers. The daughter cells are genetically identical to one another. Meiosis II starts without any more replication of the chromosomes.
Between Meiosis I and Meiosis II chromosomal replication does not take place. Meiosis I goes directly to Meiosis II, and it does so without going through an interphase. In Meiosis II, chromosomal numbers that have already been reduced to haploid (single) by the end of Meiosis I continue unchanged subsequent to this division. Meiosis II divides each haploid meiotic cell into two daughter cells.
Therefore, the aforementioned production of four sex cells or gametes has occurred.
Mitosis- a form of nuclear division in w/c one nucleus divides to form two nuclei, each containing the same chromosome number with identical genes. Occurs in 4 stages called: Prophase, Metaphase, Anaphase and Telophase.
-associateed with somatic cells only.
single celled organism- asexual reproduction
multi celled organism- growth and repair
Meiosis- a form of nuclear division in which the four daughter nuclei contain half the chromosome number of the parent nucleus.
-associated with sex cells ONLY.
functions: allows for sexual reproduction.
allows new combination of genes to be formed which will give rise to variations amongst organism
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