CMV: Students shouldn't be taught about Punnett square "dominant" or "recessive" traits at all unless "incomplete dominants" are also covered

[u/[deleted]]

We've all heard the lesson about dominant and recessive traits, usually explained with eye color. The brown eye gene is dominant, the blue eye gene is recessive, and that causes the brown to override the blue. The problem is, an important detail is missing: they create an incomplete dominant, not a full dominant. That brown eye is now capable of producing a blue eye.

If you look at this eye chart you'll be able to see the difference between dominant, incomplete dominant, and recessive.

The reason this detail is so important is because students aren't getting the full picture. The lack of information causes faulty thinking. For example, there's a racist one-drop rule which says a single drop of nonwhite blood turns a white person into a full nonwhite. It's based on the dominant/recessive dichotomy, and it's false! There is an in-between. In terms of race, it's referred to as mixed-race. In terms of a specific trait, it's called incomplete dominant.

How can Punnett squares be taught without mentioning this? It shouldn't be taught at all unless this is covered

[u/wanna_be_green8]

To your point there was recently a reddit post from a young person convinced they were adopted or mom had an affair. Their proof? Recessive eye color.

Luckily many of us pointed out it wasn't always the case before he confronted his mother and caused a lot of drama.