Meiosis and Sexual Life Cycles: Factors that Contribute to Genetic Variation

  1. a.      __create different versions of genes known as __
                                                                  i.      Once differences arise, __of __during __ produces variation that results in each mumber of a sexually reproducing population having a unique combo of traits
    • Mutations
    • alleles
    • reshuffling
    • alleles
    • sexual reproduction
  2. a.      Sexually Reproducing organisms
                                                                  i.      Behavior of chromosomes during __ and __ is responsible for most variation           
    1.      __ (one type)
    a.      Random orientation of pairs of homologous chromosomes at __ produces genetic variation
                                                                                                                                          i.      Metaphase I: pairs (one maternal and one paternal chromosome) are on __

    1.      Orientation toward poles is __
    a.      Due to independent positioning at __, first meiotic division results results in sorting of __                                                                                                                                                                                                              i.      Independent assortment
                                                                                                                                                                                                                ii.      Each daughter cell is one outcome of possible combos
    b.      To determine number of possible arrangements: __ (humans __)= 8.4 million
    • meiosis and fertilization
    • Independent assortment of chromosomes
    • metaphase I
    • metaphase plate
    •  random
    • metaphase I
    • maternal and paternal homologs into daughter cells
    • 2n
    • 223
  3. 1.      Crossing Over
    a.      Produces __chromosmomes, individual chromosomes htat carry genes derived from two different parents
                                                                                                                                          i.      In meiosis in humans, an average of __ to __ events occurs per chromosome pair, depending on __of chromosomes and __
    • recombinant
    • one to three crossover
    • size
    • position of centromeres
  4. Crossing over begins in __ as __ pair loosely along their lengths

                                                                                                                                          i.      Each gene aligned with corresponding gene on other homolog
    1.      DNA of two __—one maternal and one paternal—is broken by specific proteins at corresponding points, and the two segments beyond the __ are each joined to the other chromatid
    • prophase I
    • homologs
    • nonsister chromatids
    • crossover point
  5. Crossing over in Metaphase II

     a.      Metaphase II
            i.      Chromosomes contain one or more __chromatids and can be oriented in two alternative, nonequivalent ways with respect to other chromosomes, because sister chromatids no longer __
    b.      __
     i.      Different possible arrangements increases number of genetic types
    • recombinant
    • identical
    • Meiosis II
  6. 1.      __
    a.      223 (8.4 million) possible combinations
                                                                                                                                          i.      Fusion of gametes during fertilization will produce zygote with any of about __ (223 x 223)

    • Random Fertilization
    • 70 trillion
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Meiosis and Sexual Life Cycles: Factors that Contribute to Genetic Variation