What is the science behind blonde hair?
I've heard it's the same thing as brown hair genetically except the distribution of a brown eumelanin is more sparse. Is this true?
Or maybe there are other differences?
If so, does this rule also applies to red hair?
To grey eyes? Hazel eyes? Light brown skin?
I'm not quite sure, because I'm not an expert in this area.
Should we create a separate board for soft science majors?
*crickets*
Anyone?
>>8111278
The genetic basis for human pigmentation is not that well established yet. If I remember right the best predictive models include something like a dozen polymorphisms in six genes, but their predictive power is only reliable for eye colour, with skin and hair colour models being less reliable.
I'm a bioinformatician and do genomics but I've done very little work with human data.
>>8111449
thx
>>8111287
What's with his lower lip?
Eumelanin is black and blue, and pheomelanin is red and yellow. MC1R is the molecule that binds to melanocyte-stimulating-hormone, and when the MC1R molecule on a melanocyte touchs MSH it ceases to produce pheomelanin and begins producing eumelanin.
Blond people are defined by having a so-called allele of the gene that codes for the MC1R molecule. This allele produces a broken MC1R molecule that can't bind with MSH. If it can't bind to MSH, eumelanin production can't begin.
A human is so-called haploid, meaning that every chromosome is doubled during cell division. During reproduction, diploid sperm and ova with only 23 chromosomes carry one MC1R allele - either the broken blond one, or the functional black one.
A real person's melanocytes aren't all blond or all black - some of the cells produce eumelanin, and others don't. Aging involves the death of melanocytes entirely, leading to gray hair. It's thought that blond hair evolved from old people with damaged DNA coding for MC1R, who passed in their damaged gene.
Blond hair is recessive because if you breed with someone with a functional MC1R allele, and the child inherits even one copy of the functional MC1R gene, their melanocytes can produce functional MC1R molecules and so produce plenty of eumelanin.
>>8112845
>A human is so-called haploid
>diploid sperm and ova
>single gene model of pigmentation
Please stop talking about things you don't understand.
>>8112910
>A human is so-called haploid
We are. On occasions, some of our cells don't inherit two copies, or more than one set of copies is produces. Some cells in the liver often have dozens of extra chromosomes.
I gave the textbook answer, but I agree that the reality is more complex.
>diploid sperm and ova
Gametes have only one copy of each chromosome, which is the definition of diploid.
>single gene model of pigmentation
The other genes regulate the production of MSH, and every other gene involved is also involved in the synthesis of tens of thousands of other proteins.
The OP asked for information on how genes make hair color. He wants to know how the factory makes the product - not how the factory is made.
I appriciate your point, and honestly I'll say that understanding the details means everything. At the moment, I'm studying the web of genes that control waist size, fat distribution and the length of the vertebral column.
Why don't you tell us about the web of genes related fo MC1R? Are there endogenous MSH antagonists? How do melanocytes use Sonic Hedgehog and Robotnikin? What other cell types and molecules contribute to hair color? How does EDAR relate to this, since it changes the strtucture of the hair and thus how it absorbs, reflects and refracts light?
Viking aliens
>>8112991
>Gametes have only one copy of each chromosome, which is the definition of diploid
No, that is the definition of a HAPLOID.
How can you claim to know anything about a topic when you can't get the most basic terms right?
