Conclusion
From the four human traits investigated, it is clear that what biology textbooks and classrooms teach is not true. Earlobe attachment, cleft chins, hitchhiker's thumbs and tongue rolling are all not simple two-allele characters. Rather, they are most likely determined by a multitude of alleles and also affected by environmental factors. So back to the question:
Should classrooms change the way they teach basic Mendelian genetics?
Yes! Not only are current textbooks and classrooms teaching students the wrong information, they may also be causing families to question if certain members are actually a part of the family. But these facts are all just myths.
The reality is that two parents with attached earlobes can have a child with free earlobes. Two parents with smooth chins can have a child with a cleft chin. Two parents with straight thumbs can have a child with hitchhiker's thumbs. And two parents who can roll their tongues can have a child that cannot roll their tongue.
Should classrooms change the way they teach basic Mendelian genetics?
Yes! Not only are current textbooks and classrooms teaching students the wrong information, they may also be causing families to question if certain members are actually a part of the family. But these facts are all just myths.
The reality is that two parents with attached earlobes can have a child with free earlobes. Two parents with smooth chins can have a child with a cleft chin. Two parents with straight thumbs can have a child with hitchhiker's thumbs. And two parents who can roll their tongues can have a child that cannot roll their tongue.