Figure 2.

A sample incomplete pedigree chart to illustrate sex determination. Each vertical line indicates an offspring. By tossing a coin to decide whether the father's X or Y chromosome is passed onto his offspring, the gender of the offspring is determined, and square, for male, XY, and circle for female, XX, can be drawn below each of the vertical lines. Any one pedigree chart can have all male, all female or any ratio in between. For a large enough class, with ~ 30 students or more, the ratio of males to females should be close to 50:50.

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