Get the students to use shoestrings or bead strings as models of chromosomes. Different sizes of pairs will stand for the various homologous pairs and two different colors would indicate the two parents. To demonstrate crossovers the best type of beads are those that can pop into one another. The instructor should prepare the classroom by providing large sheets of paper with a circle on each to represent a cell. Clearly students will be starting with cells in late prophase, prophase I, or prophase II.
References: O'Brien, S.J. and M.Dean. 1997. In Search of AIDS-resistant genes. Sci. Am. 227 (5): 44-51.
Weaver, R.F. and P.W. Hedrick. 1992. Genetics, 3rd ed. Dubuque, IA: WCB/McGraw-Hill.
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