Review behavioral objective 8. The answer to the question on the preceding page is included in the readings indicated by G-5. Cells spend most of their time in the interphase stage. The time cells spend here may vary from five hours to many  years. Most of the cells in your body cells (somatic) are in the interphase stage. More specifically they are in the G-1 stage. Just before mitosis the DNA content doubles. This occurs during the S stage of .mitosis. The reason for this that at the end of mitosis two daughter cells will form with the same amount of DNA in each cell as the single mother cell; therefore, a doubling of DNA must occur before the chromosomes form and segregate into two cells. Examine the two figures below. The top figure represents a cell during the G-1 stage and the bottom figure represents a figure during the G-2 stage after DNA synthesis (S stage). Note the doubling of DNA  in the bottom figure. Draw and explain these figures in your notes. 

                       k- G-1 stage  
 

                                                    S stage DNA replication 

                          k- G-2 stage  

Note: The DNA in the G - 2  stage has not only doubled but the two strands are connected. 
 
 

9. Study the figure above. How many DNA molecules are their in the G-1  and G-2 figure respectfully? 

     a. 12  :  24                         c.    6  :  12 
     b. 24  :  48                         d . 24 :   24 

Press here to check answer.   press  
 
 
 
 
 
 

10. Most of the epithelial cells that make up your skin are in which stage of the cell cycle? 

     a. S                                     c. G2 
     b.Mitotic                             d. G1 

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11. How many DNA molecules and chromosomes are present in the human somatic (body) cell during the "G1" and "G2" stage of interphase? (human somatic cells are the normal diploid cells that make up the human body) 

           G1                G2                                              G1                   G2 

     a. 23 : 46        46 : 92                                        c. 46 : 46            46 : 46 

     b. 46 : 23        46 : 23                                        d. 46 : 46            92 : 46 
 
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G-1stage                    G-2 stage  
 

 Examine the figures above showing interphase (G-1) and interphase (G-2) after DNA synthesis. .  In your notes draw these figures showing the three pairs of chromosomes. 

Now add genes to these chromosome pairs.  Use the letters "A and B"  to represent the genes. Add to the  long red and blue homologous pair the genes "A" and "B".  Indicate  one of the homologous pair "A" genes with an upper case A and it's homologue with a lower case a. Indicate one of the homologous pair "B" genes with an upper case B and it's homologue with a lower case b.  Compare your answer to the figures below. Your will be asked to follow this assignment through the mitotic stages of cell division during a  later lessons.. 

Check your figure to the one shown below. Click here.  click 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

                              G-1 G-2 
 
The letters represent genes on the DNA molecules. Note the position of  the genes in the G-2 figure. The mother DNA with its genes synthesized a daughter strand with the same genes and remained attached to the mother DNA. This concept is very important for you to understand mitosis and meiosis. Draw these figures in your notes along with the letters designating the genes. To check the correct observation you must answer the following question correctly to move to the next page. 

Which of the following show the correct representation of the genes on its designated DNA molecule  in the G-2 stage?  The correct answer will move you to the next page.

                a ) aaBB and  AAbb 
                b ) aabb   and  AABB 
                c ) AaBb  and AaBb 
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