|
I bought two decks of cards the other day at the dollar store with the intention of teaching my students the finer points between mitosis and meiosis. Most of the teachers I know don’t attempt to distinguish between the two in general biology and anatomy and physiology courses; the students are required to learn the phases and recognize them on onion slides or whitefish blastula slides. I want my General Biology students to know the mechanics of the two processes, so that when I teach genetics, properties such as segregation of alleles and independent assortment will make more sense to them. The following will show a way to teach mitosis and meiosis to the students mechanically. This demonstration can first be done in a lecture, and the students can practice during the laboratory session. Picking two pairs of chromosomes, one maternal and one paternal is the easiest way to start.
Pull out an ace of hearts, an ace of spades, a two of hearts and a two of spades. The hearts will represent maternal chromosomes, the spades, paternal chromosomes. Show them to the students and tell them these represent two pairs of chromosomes (four cards). Now from your other deck take out the same cards and lay them over the first set of four. Voila DNA replication! Line up the four sets of duplicated cards (or eight chromatids) end to end the long way across the table (metaphase). Then, pull the cards apart, simulating anaphase. Bunch each set of separated four cards into a little pile (telophase), and tell them to imagine cytokinesis.
To simulate meiosis, use the same cards, except during metaphase, have the duplicated card piles line up in two horizontal rows—the two piles of aces touching each other, next to the two sets of twos touching each other (homologous chromosomes). Now pull the two sets of cards away from each other, without separating them into individual cards (Meiosis I, anaphase I, segregation of alleles—point out that now the two sets of cards are different from each other). Now take this first set, and repeat the separation as in mitosis (Meiosis II).
The students can then alternate the positioning of the cards so that when they do the segregations one time, each of the four cells will end up with only maternal OR paternal chromosomes, and when they line the cards up the opposite way, each cell will contain a mix of maternal and paternal chromosomes (independent assortment). Of course, my favorite assortment is of the chocolate variety---perhaps there is some type of demo we could do there! The students can then next add additional “chromosomes” and demonstrate both processes to each other in the lab. Just watch that they don’t settle down into a little poker game!
   
|
