Mitosis: Self-replicating Cells 

You started out as a single cell called zygote. This was formed by the union of a sperm and an egg. This single cell divided by mitosis and has continued to divide for several years producing trillions of cells. These cells are used for growth and replacement of dead cells. All of the daughter cells formed from this original mother cell containing the same number of chromosomes as one another and the original mother cell.  Also, all of these cells are genetically alike.

 

Read behavioral objective 6. One of the characteristics of living organisms is that they must be capable of reproduction. Many lower forms of organisms (amoeba, paramecium, algae ) reproduce asexually. The cells simply divide by mitosis which produces two cells which are genetically alike. Those organisms that reproduce sexually, form sex cells (gametes) by a special type of cell division (meiosis). These gametes have only one half the number of chromosomes as the original mother cell. The gametes combine (fertilization) to form a single cell (zygote) that divides to grow by mitosis into an embryo. Growth and the replacement of damaged or dead cells require mitotic cell division. 

Meiosis will discussed later in this miniunit. Using your text write in your notes the definitions for gametes, zygote, somatic cells and sex cells.

 

20. If the figure above represents mitosis and the mother cell "top row" contains 23 pair of homologous chromosomes, how many chromosomes and homologous pair will be located in the daughter cells located in "the second row"? 

   a. 23 : 12.5       b. 46 : 23           c. 92 : 46         d. 26 : 26 
 
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21. Which of the following processes does NOT include cell division? 

a. Formation of an embryo from a single cell zygote. 
b. Growth of a lateral branch on an oak tree. 
c. Regeneration of a tail which was removed from a newt. 
d. Growth of a hair follicle. 
e. Formation of a cancerous tumor. 
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22. Which of the processes below represents meiosis? 

a. Formation of new skin cells. 
b. Formation of cancerous tumor cells. 
c. Formation of human sperm cells 
d. Formation of human egg cell. 
e. Both c and d above. 
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This is the end of lesson two. Click here to go to lesson three: Cell Cycle: Eukaryote Cell. 
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Created by the Center for Learning Technologies, Academic Technology Services. 
Last modified October 22, 1997.