Life Cycle - Human Biology (6A)
Post Lab 

  • Exploring how a cell divides. 
  • Comparing mitosis and meiosis.
  • centriole
  • chromatin
  • chromosome
  • meiosis
  • mitosis
  • worksheet
  • coloring pencils
  • Internet

Students use a worksheet to compare meiosis and mitosis.



Students need to discover why all cells cannot produce babies.  Mitosis is the process whereby cells exactly duplicate themselves.  Both old and new human cells contain 46 chromosomes.  During meiosis, which involves the sperm and egg cells, each cell has 23 chromosomes.  When the sperm and egg unite, the fertilized egg will have the normal number of 46 chromosomes, half from the mother and half from the father.  

In the worksheet we have the students trace the stages of mitosis and meiosis.  Before mitosis begins, the nucleus contains chromatin (protein + DNA).  As the cell begins to divide, the chromatin begins to condense into 23 pairs of x-shaped structures called chromosomes.  The centrioles (whose function is not fully defined) move and spindle fibers begin to develop around them.  Each of the chromosomes become a pair of identical chromosomes.  The centrioles are at opposite sides.  The spindle fibers stretch from one side of the cell to the other.  The chromosomes pair across the center of the spindle.  The two halves of each chromosome pair separate and move to opposite sides of the cell.  Two new nuclear membranes develop.  The cell begins to break.  The two new cells are complete.  

During meiosis the story is a little different.  There are different avenues for the female and male sex cells.  Meiosis is the process that produces 23 chromosomes (haploid) from 46 chromosomes (diploid).  Meiosis is long and complicated and frequently takes days to complete instead of hours or minutes as does mitosis.  

  1. Go over the information on the worksheet emphasizing mitosis and meiosis. Mitosis is just the dividing of a cell into equal parts. The two types of meiosis one involving the sperm and one involving the egg.  Meiosis is characterized by going through two phases of cell division.  The first phase closely resembles mitosis.  One sex cell produces two sex cells in the first phase.  The two sex cells will then divide again to produce 4 sex cells.  In females, however, only one egg is produced (the remaining 3 cells are called "polar bodies" and their function is not positively known.)  The resulting sex cell will have one half of the normal number of chromosomes (23).  Meiosis only occurs in sex cells, not in other cells.
  2. Instruct students to using coloring pencils to make the worksheet more readable. 
  3. Use the Internet if students are unfamiliar with cell structure.  Search under “cells” or “genes” to look for information. 

  [Back to Life Cycle Grid]  [Back to Human Biology (6)]