Mendel's peas were either tall or short, either yellow or green. Most of what you see in people is messier than that, and it follows rules too.
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Students will explain incomplete dominance, multiple alleles and polygenic inheritance with one example each, and tell which pattern a described trait follows.
In incomplete dominance neither allele fully covers the other, so the heterozygous offspring looks in between. It isn't blending: crossing two pink flowers brings back red and white, which a true blend could never do.
A person still carries only two alleles of the ABO gene, even though three exist. And a polygenic trait gives a smooth range of results, not a few separate groups.
🚨 Calling pink a blend. The test is what the next generation does: if the parents' original looks come back, the alleles stayed separate.
Counting three alleles in one person. The ABO gene has three forms in the population, but each person has just two of them.
Line the family up by height, or measure everyone in the house, and see that there's a smooth spread rather than a tall group and a short group. That is polygenic inheritance, and seeing it makes it plain.
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Before You Start
The words this lesson uses. Tap a card to see what it means, then come back to them whenever a question uses one.
Part One
Questions about the story you just read. Pick your answer straight off, or press Find it in the story if you would rather hunt for the sentence first.
Part Two
The word cards are at the top of this page. Look back at them as often as you need, then answer.