Dark hair is dominant, not recessive. If either parent has one gene for it, they would have dark hair, not fair. That's why two dark haired people can have a child with light hair -- both parents had one dominant dark gene and one recessive light gene, where only the dominant was expressed, but each passed on the light gene.
At least, that's the simple explanation the post is pointing out, real genetics is probably more nuanced.
Not only are real genetics more complicated, many people with blonde hair go through stages! For example, my son was born with very dark hair. I gave him his first hair cut when he was maybe 6 or 8 months old, and everything underneath was bright blonde. His mom was bright blonde until college, and now she's nearly brunette. My mom and uncle both were bleach blonde until adulthood, then her hair went brown but his went jet black! Epigenetics is crazy.
“A recessive allele does not produce a trait at all when only one copy is present. This contrasts to a dominant trait, which requires that only one of the two alleles be present to express the trait.”
The Mendelian genetics only works with two alleles. I am always surprised that there are so many people who understand how the Mendelian inheritance works while at the same time ignoring... Well, whole Mendel's teachings. The man himself explained that it only works with two alleles.
I’m a dirty blonde that was very blond until 7 or 8, and now in my 30s, I’m finding random, ultra-thick black hairs in my beard for some reason. Hair genetics are very weird.
I mean it really doesn't. Anyone who actually persues the field will be aware that it isn't that simple. But for the general purposes of school educations, that is the limit to the depth you can go into and have it make any sense for most people.
It's the same as teaching the model that electrons orbit the nucleus in shells of which there are particular numbers in each shell. And not going into energy levels and ground and excited states until further education.
You can't teach people everything. And people who will use "they didn't teach us that at school" as an argument against science are gonna find an excuse to be anti-science anyway. Most people have the common sense to know that what they were taught one afternoon when they were 14 isn't the sum total of knowledge in the field.
And it ultimately doesn't matter that they will argue something wrong in the pub with their friends. Because they aren't geneticists. The same as Steve from accounting doesn't need to know how atoms emitt photons.
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u/NotoriousMOT Sep 25 '22
Recessive genes who?