Mini-Meiosis Lab Activity

Meiosis (pronounced mi-o-sis) is the process by which one diploid eukaryotic cell divides twice to generate four haploid cells. In animals, meiosis always results in the formation of gametes. The word meiosis comes from the Greek meioun, meaning to make smaller, since it results in a reduction in chromosome number in the gamete cell.

Before doing a phase, use the knife to carefully separate cream from one cookie side. Be sure to leave all the frosting (cytoplasm) on one cookie side; this will represent a cell (i.e. spermatogonium or oogonium).You may dispose of the unfrosted cookie in any manner you see fit.

Homology is to represented by color. You will start off by creating a parent cell with a 2n = 4, before the S phase (DNA duplication) begins.

To do this, select (4) brown grains of rice and (4) white grains of rice and put (2) of the brown grains together, end-to-end and (2) of the white grains together, end-to-end in the frosting (cytoplasm). Do the same procedure with the remaining grains. Now, with the toothpick, draw a nucleus around the (4) rod shaped structures. Add (2) pairs of centrioles (candy) at one end (pole) of the cell.

To start Prophase I, you will need to select 8 brown grains and 8 white grains. Create X chromosomes with the rice by using the grains as arms so that you have (2) brown X chromosomes and (2) white X chromosomes. Being that this is Prophase I, this is where you need to show: tetrads and crossing-over (with at least 1 of the tetrads (see next step on how to do this))

Crossing over must be demonstrated during Prophase I. To do this, select any homologous pair of chromosomes (brown or white). As tetrads, have them cross over at least one arm each by placing the arms on top of each other. The following phases do not need to show this.

Place the cake decorating candy spheres (centrioles) in their appropriate places and using a toothpick, draw asters and spindle fibers. The toothpick can also be used to demonstrate nucleus and nucleolus degradation and reforming by poking around small dots in the frosting (cytoplasm); you can use the toothpick to move the grains, too.