Prophase I  - 
        1. Nuclear membrane pulls apart and becomes part of  the E.R. and the 
            nucleoli  dissolves  (disappears). 
        2.  Each DNA molecule twists and coils back on itself  to form  rod shaped 
             chromosomes. 
        3. Centrioles separate and  a new centriole develops at the base of each 
             parent  centriole  forming  two centriole organizing centers. These 
             centriole organizing centers than migrate to poles on opposite  sides of the 
             nucleus. 
        4. Spindle apparatus fill form from microtubules. Spindles will form between 
           centromeres of  each chromosome and  each  centrilole organizing 
           center, spindles  will form  between both  centriole organizing centers, 
           spindles  will radiate out behind   the centrioles and form asters. 
        5. The chromosomes at this time are attracted to one another in the following 
            manner. 

            Homologous  chromosome pairs are attracted to one another.  This process is called    synapsis and the resulting groups of four chromatids is called  tetrads. Locate the three sets of  tetrads  in the figure below. Draw and label this figure in your notes. 

 
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1. The answer is "c".  Crossing over can only occur during synapsis when tetrads are formed. Are tetrads formed during mitosis and meiosis II? Check you notes. 

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2. The answer is "e". The genes on the same chromatid are linked and will remain linked unless crossing over occurs. 
 
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3. The answer is "e".  Examine the figure below  to see how the genes segregated out during meiosis. Note that only the inside chromatids crossed over. Write the definition of a chiasma in your notes. 
                                 crossing over  
Identify the chiasma in the bottom figure. 
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4. The answer is "b". This is very important in understanding the differences between mitosis and meiosis. Review in your notes the drawings  of anaphase during these three stages. During mitosis sister chromatids split at the centromere and are pulled to opposite poles, during meiosis I homologous chromosomes are pulled to opposite poles (sister chromatids remain attached) and during meiosis II sister chromatids split at the centromere and are pulled to opposite poles, since this is a mitotic division. 

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5. The answers are: Yes, a diploid cell containing 24 chromosomes can undergo mitosis forming two cells each with 24 chromosomes. Yes a diploid cell containing 24 chromosomes can undergo meiosis  forming four  cells each with 12 chromosomes. 

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6.  The answers are: Yes, a haploid cell  containing 12 chromosomes can undergo mitosis forming two cells each with 12 chromosomes. 
 
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7. The answer is: Yes, a diploid cell containing 24 chromosomes can undergo meiosis  forming four  cells each with 12 chromosomes. 

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8. The answer is: No, a haploid cell  containing 12 chromosomes can not undergo meiosis because its chromosome number has already been reduced by one half (contains only one of each homologous pair). 

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9. The answer is "b".  A diploid cell containing six chromosomes contains three homologous pair. 

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10. The answer is "c". The cell contain three sets of two different types of  DNA molecules. There are eight ways to arrange these into sets of three DNA molecules per cell. 

                AaBbCc  = one cell before mitosis (diploid) 

           ABC,  aBC, 
           AbC,   abC,   =  8 cells after meiosis (haploid) 
           ABc,    aBc, 
           Abc,     abc, 
 

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10a The four types of gametes are shown in the figure below. The two top gametes (RS  and rs) are the noncross overs and the bottom two gametes (Rs and rS) are the result of crossing over. ,
 
  
 
 
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11. The answer is "a". You may want to look at the figure in your text showing  Chlamydomonas gametes and the human sperm and ovum gametes 
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12. The answer is "c".(hint: secondary spermatocyte consists of two cells; which stage  of  meiosis consisted of two cells) 
 

 
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13. The answer is "b". The spermatid is haploid, therefore only 23 chromosomes. 
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14.  The answer is "c". Check your figure showing the male reproductive system. 
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15.  The answer is "b". Check the chart you made concerning the male hormones. 
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16.  The answer is "b". Check you drawing of the human sperm. 
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17.  The answer is "d". Check you drawing of the human sperm. 
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18.  The answer is "c". Check the chart you made concerning the male hormones. 
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19. The answer is "c". Study the chart below and identify where the various stages of meiosis would occur. 
 

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20. The answer is "b". The ootid is haploid. 

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21. The answer is "a". The primary oocyte is diploid. 
 

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22. The correct answer is "a". One egg or ovum and two  or three polar bodies. 

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23. The answer is "b". Polar bodies are haploid 

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24. The answer  is  "b". Check the table you made concerning female hormones. 

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25.  The answer  is  "c". Check the table you made concerning  female hormones. 

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26. 
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27.. 
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28. 
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29. 
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30. 
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