Blonde hair and red hair are recessive traits, meaning that they require two homozygous recessive alleles to be expressed (in this case, bb or rr). What hair color would the child of a blonde and redhead have since there is a 100% chance of them being br? Would one recessive allele dominate over the other? Are there real life examples of blonde + redhead and what were the resulting children?
I am absolutely not a scientist/geneticist so please be correct any factual inaccuracies I may have made!!
In: Biology
Hair color is not just dominant/recessive like we’re taught in schools. Its a very complex interaction of dozens of genes that are hard to predict based only on the parents
While the whole “dominant and recessive” thing is super useful for learning the concepts, the reality is that genes are way more complex and tend to be a mixture of like, kind of dominant and kind of recessive but sometimes they both express to some degree. There are [at least 124 genes that contribute to hair color](https://www.sciencedaily.com/releases/2018/04/180416121600.htm). Ultimately, it comes down to the very unique combination in that person.
It also has to do with past generations. Both of my parents had black hair and I’m solid ginger. 🙂
I believe the term often used for such hair is “strawberry-blonde”.
Of course genetics isn’t as simple as many of us were taught in school, and variations that you wouldn’t expect can occur. My brother is blonde – but a few red hair often would show up in his beard if he grew it out enough. He isn’t “strawberry-blonde” though. One of our GREAT-grandparents supposedly had red hair (but all we have are black and white photo’s).
As others have said, hair color isn’t a simple case of dominant vs. recessive. In fact, very few traits follow those simple rules of Mendelian genetics, but that’s the way most high schools explain genetics to keep the concepts digestible for beginners. Most traits involve multiple genes that have complex interactions, and it can be hard to predict the outcome.
My dad was a redhead, mum was blonde.
I’ve got red hair, as do some sisters. One sister has blonde hair.
Not sure what the genetic explanation is, but that’s the end result either way.
The notion of recessive traits is a gross oversimplification.
To offer a slightly less simplified explanation which is still not telling the whole story: the genes for red and blond are separate things. You can have both the genes for blond, and the genes for red. In fact you can have the genes for black hair and the genes for red. The red hair genes are a separate thing that makes hair redder then the normal hair color would be based on the other genes.
This generally means that it’s only noticeable for people that have both blond hair genes and the red hair genes, because otherwise you can’t really see the redness. This makes red hair genes slightly different than the “recessive” trait that they teach in schools. Its effect can get covered up rather than replaced entirely.
So in this case your talking about 2 people that both have blond genes, one of which also has red. The result will be someone with red hair.
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