Cell, Socks, and Sex
This is a fun, easy way to teach the process of mitosis and meiosis. This will strengthen vocabulary concepts like homologus pairs, diploid, haploid, tetrad and many others. This lesson will also clear up concepts like sexual determination, trisomy and even twining.
Four or five pairs of socks. The more used looking the better.
I start with a long, striped piece of fabric that has been twisted hundreds of times to represent chromatin material. (Use a mixer tied to one end of fabric and the other end of the (five yards by five inch) fabric to something very stationary.) I might discuss histones and nucleosomes and how much information is coded onto the chromosomes. Next, I blow up a large, clear balloon, which I have preloaded with two identical socks, joined at the center with a Velcro "centromere". I blow up the balloon, which represents the nuclear membrane, then I pop it. The two socks represent a chromosome that has duplicated.
I use socks with colored stripes, so that I can easily make reference to the genes in them, but add the idea of homologous chromosomes and alleles. I add another two socks "chromosomes" (which has finished prophase), [this is two pairs of socks for a total of three,] and I line these all up---down the middle of my body, from the top of my head to my knees (metaphase), and then pull them apart (anaphase) to the poles--my hands (teleophase). (One pair goes on my head, one pair is tucked into my neckline, another into my waist.) Each hand now has the chromatin material of an identical daughter cell.
I use a similar approach to teach meiosis. I use two similar, but not identical, socks, to represent homologous pairs. One might have blue striped "genes," while the other allele has red stripes. (A non-homologus pair would be socks that have wider stripes or are sport socks as opposed to bobby socks.) The homologous pairs duplicate so I have two similar pairs, then come together (prophase I); I now have four socks, showing a tetrad and possibly a crossover. I again line this up, down the middle of my body (metaphase I) and separate (anaphase I). I finish demonstrating meiosis II to get four gametes.
Now, I add the sex chromosomes to the original autosomal chromosomes. I start with "XX," which is represented by a pair of little girlUs long pink knee socks. When I finish, I have used two pair of pink socks to make four gametes, each with two autosomal chromosomes and one sex chromosome, "X." I set the "eggs" aside and demonstrate spermatogenesis, using one blue knee sock (Y) in a much smaller size and another pink sock for the X, thus making an "XY" pair. The spermatogonium with the smaller, blue "Y" chromosome does its thing, and I soon have four waiting sperm.
While singing Sthe race is on and here comes Clyde in the back stretch,S the sperm swims a bit and meets the egg. (I have earlier mentioned that they have been properly married.) I do this several times, using different sperm ("X" or "Y") and different eggs, which have differently colored striped genes. The students see how sex is determined (as opposed to the students who are determined to have sex) and the variability of sexual reproduction.
I then extend the activity to demonstrate nondisjunction, trisomy, haploid and diploid chromosomes, alleles, dominant and recessive autosomal traits, and homologous pairing. Often, throughout the genetics lessons, when I receive questions, I just pull socks out of the box and have the students think it through to answer their own question.