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Preston Biology 22 January 18, 2008 Weekly Study Question # 1 Explain the crossing over of chromosomes; continue on to describe why this is critical and what would happen, to the offspring, if this did not occur? The crossing over of chromosomes takes place during late prophase 1, the non- sister chromatids begin to separate at many points along their length, certain locations stay joined therefore creating an “x” shape called a Chiasma. Crossing over is important because it is said that the physical exchange of paternal and maternal chromosomes occurs at the chiasmata. The paternal and maternal chromatids break and rejoin at each
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Unformatted text preview: chiasma, producing chromatids that have both maternal and paternal segments. This exchange is vital because it results in genetic recombination; this dramatically increases the genetic variability of gametes produced by meiosis. If crossing over does not occur the chromosomes would not have a mixture of maternal and paternal alleles, if meiosis were able to continue without this step, more homologous chromosomes would be formed. Genetic recombination will not occur without crossing over, therefore the alleles will all be the same, as a result of this the offspring could have difficulty reproducing or surviving....
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This note was uploaded on 05/23/2008 for the course BIOL 22 taught by Professor Preston during the Winter '08 term at Santa Clara.

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