4.03 Genetic Park: Stages of Meiosis

The Honors student will:

• recognize the stages of meiosis
• summarize the special events of prophase I of meiosis

Take a look at this diagram. On the left you see a double stranded chromosome as it is just before the cell splits for the first time in meiosis. That's right, there are actually two divisions that take place in meiosis.

• The first division results in a doubling of each chromosome - the double strand; and then the chromosomes split into a single strand. Each single strand of the chromosome is called a chromatid.
• The second division results in the separation of these doubled chromosomes, and results in the production of the sex cells.

As you get started on this extension, there are some words to make sure that you learn and add to your vocabulary sheet.

• Homologous chromosomes - The pair of chromosomes in a diploid cell that have the same overall genes - that is they contain the "code" for the same traits. One chromosome in the pair comes from the father and one from the mother.
• Chromatid - A single rod-shaped chromosome before it is replicated. Most of the time chromosomes are pictured in the shape of an "X". The two rod shapes (called sister chromatids) are the original chromosome and the copy connected in the middle to give it the x-shape.
• Crossing over - Where two non-sister chromatids exchange genetic material. A few genes can be exchanged or none at all. This leads to the uniqueness of each sex cell.

Keep these words handy as you continue discovering how organisms come to be so unique.

Working Through Meiosis

To get a feel for the process of Meiosis you are going to work your way through a tutorial that covers the two divisions, and the stages within the divisions. You'll notice that the stages are similar to mitosis, yet very different. As you take a tour through the Meiosis tutorial (from Sumanas, Inc.) complete the following tasks. Work through the introduction, the animations, the conclusion and then take the quiz. Make sure that you can work through each stage and are able to explain what is happening in that stage. Prophase I is a very important phase of meiosis. A lot of genetic mixing will go on in this first stage of meiosis. Be prepared to describe how prophase I leads to genetic variations of offspring. You may also want to take some Notes. In any case, be prepared to explain the stages of the process!

You may also want to go to the Access Excellence site and print the diagrams of the phases of meiosis. Use these diagrams to help you as you go through the tutorial above a second time.