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Red Head Siblings?

I know that in order to have red headed offspring, both parents must have the (recessive) trait. That said, I’m curious about this and haven’t found a straight answer that requires me to go further into genetics than I care to understand...

Is it possible for two parents, both with the recessive trait, to have one child with red hair and one without? Or would they both have red hair? Basically, is the whole red hair thing “all or nothing” for offspring or can you still have children with multiple different colored hair? 

7 Answers

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  • 3 months ago

    Two parents, each heterozygous for the red hair allele, can have children with red hair and children with brown or black or blonde hair.

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  • Anonymous
    3 months ago

    Red hair is the result of having lots of the pigment phaeomelanin on the hair but no eumelanin (dark brown to black pigment). Most people around the world have dark brown to black hair because they have lots of eumelanin on their hair.  Blond hair is the result of having no eumelanin but a small amount of phaeomelanin on the hair. To have either blond or red hair, it is obvious that the genes that produce eumelanin inside hair follicles must not be working (homozygous recessive) in addition to having genes that produce red hair.

    Your question does not state whether both parents are red headed or not. They can for example carry the trait for red hair (if it is recessive) but still have dark hair if they are heterozygous (having only one copy of the redheaded gene). The inheritance of red hair is not completely known but it is definitely controlled by multiple genes. For example, a red haired person must be homozygous for the inability to produce eumelanin, AND his/her other genes must code for a lot of pheomelanin instead of just a little because otherwise he/she may end up with blond hair instead of red hair. Apparently there are also multiple genes that control red hair, so even if both parents have red hair, their young may not even have red hair. It may be the reason why redheaded people are so rare. Let's suppose that 2 separate genes are needed for red hair. That means both parents must be homozygous recessive for both genes to have all redheaded children.

    • Zirp
      Lv 7
      3 months agoReport

      "Let's suppose that 2 separate genes are needed for red hair. That means both parents must be homozygous recessive for both genes to have all redheaded children."
      err...no. it means both parents have to be carriers of both recessive alleles and happen to both pass on both to the same child(ren).

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  • Zirp
    Lv 7
    3 months ago

    "in order to have red headed offspring, both parents must have the (recessive) trait"

    no, they must both CARRY the recessive ALLELE [if it really is that simple]

    "Is it possible for two parents, both with the recessive allele, to have one child with red hair and one without?"

    yes, definitely.

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  • 3 months ago

    Yes, it's possible for two red-headed parents to have one child with and another without red hair.

    Mendel did some very important, foundational work that led eventually to modern genetics.  But his recessive/dominant calculus only works when there are only two possible traits from those alleles, and when a single gene is the only determining factor - and we know that neither of those things is correct regarding hair color in humans.  Also, he didn't know about the difference between genes and gene *expression.*

    Our knowledge of genetics has progressed quite a bit since his initial discoveries, and the field is much more complex than he was aware.

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  • ?
    Lv 7
    3 months ago

    Well, in simple terms, each parent contributes "redhead" or "not redhead" to each child, and a child has to get the redheaded gene from both parents for that to be the case. So theres only a 1 in 4 chance of the child being a redhead, because 3 of the 4 possible outcomes involve a "not redhead".

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  • 3 months ago

    To put it simply - The red hair gene is recessive. That means if the child gets one dominant gene, it will cause the child not to have red hair. The child must receive two recessive genes for the red hair trait to show.

    The being said, things are much more complicated than this simplified scenario. Genes interact in ways we can't predict. Anything could happen.

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  • 3 months ago

    My sister has brown hair. My brother and I both have red hair. Recessive traits show up if both parents contribute the recessive gene. If the gene from one parent is for some other color, that will usually dominate. 

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