Genetics question

[snooper]

Does anyone know the genetics of red hair? I know it "runs in families", but what combinations will work?

E.G. Only one red haired grandparent? Can a red haired child appear with any combination of the other 3 gps and the parents?

PS> No bottled colours involved!

 

[Colleen Thomas]

The gene for red hair is recessive I think. My father has black hair, my mother is botled blonde now, but had very dark hair when she was younger. Neither of my grandparent's on either side had red hair. My great grandfather on my mother's side had sandy blonde hair, but his beard grew in a dark red. My hair is auburn, not wholly red like carrot top, but more red than brown.

It has been a long time since I took biology, but I believe in the case of ressive traits neither parent need show the trait, they only have to be carrying it. If both have a ressive gene for red they can have a red headed child even if neither they nor their parents were red heads.

-Colly

 

[Guest]

Genetics

 

[SummerMorning]

Like they said - it's a recessive trait. It's uncertain whether it's just one gene - there could be several - and it's possible to get an odd combination, or a mutation and get red hair even if none of your parents had red hair. That's why you got people in China with red hair - where it was assumed to be either the mark of the ancestors or some evil demons (whichever you prefer - could be both ).

Anyway - generally, you don't need a single ancestor with red hair to get red hair - but the odds of getting red hair with red haired ancestors increases. The exact odds vary of course.

If both your parents have only recessive genes for red hair (simplifying): i.e. rr and rr, then you're 100% sure to get red hair (rr).

If one has rB (B = black and dominant, r = red and recessive) then it's more like 50% - one parent has black hair in this case.

If both have rB then you're 25% likely to get red hair (both parents black haired).

But that's simplifying, because I think the genes aren't that clearly identified yet - so it could be more genes. Various genes could lead to red hair, etc.

 

[gauchecritic]

With absolutely no scientific (biological or anthropological) evidence to back this up I would say that red hair can show up in any generation without reference to genes; a hair colour descendancy.

Assuming that hair colour is a function or result of geographical location (as skin tone) then we see that it is indeed true that Scotsmen have red hair, Scandinavians are blond(e) and Africans have black hair.

These are evolutionary changes (yes I know that genes are the means of evolution) and you can conclude that the potential for red hair is inherent in all genes irrespective of genealogy.

Gauche

 

[Guest]

from the Department of Dermatology, University of Edinburgh (url and refs. below) - Perdita

< A lot of people email me asking about red hair. What is it due to, and what are the genetics underlying red hair. The following is meant as a summary. Inevitably I have simplified and shortened certain aspects so pure geneticists might disapprove of some of the phrases I have used but, in essence, I think it is pretty accurate.

Skin and hair pigment is made up of different types of melanin. There are two broad groups of melanin, eumelanin, which is brown, and phaeomelanin, which is red. Somebody with dark hair will have predominantly eumelanin. Somebody with very bright red hair will have little eumelanin but lots of phaeomelanin. People with auburn hair will have some of both.

Skin and hair colour often go together, but not always. For instance, people with red hair are usually fairly pale skinned, they don’t tend to tan, they burn in the sun and are more likely to have freckles. There are exceptions however to this rule. Some people, with apparently jet black hair, also have very pale skin and freckle. We don’t understand the latter group very well.

Several years ago, I and colleagues, discovered that the melanocortin 1 receptor, a protein encoded by a gene previously discovered in mice, was responsible for the production of red hair in humans. Everybody has two copies of this gene but there are slight changes in the gene that are very common in European populations. If you have one of about four or five common changes in this gene and, one of these changes are found on both of your chromosomes, then you are likely to have red hair. A little bit of basic genetics; you have two copies of every gene, you inherit one from your mother and one from your father. If both of these genes are different, with respect to the changes that might lead to red hair, then you will have red hair. If however you only have one change, you have an increased chance of having red hair but it is not certain that you will have red hair.

Such a type of inheritance is described to by geneticists as an autosomal mode of inheritance. This means, in practice, that both your parents may not have red hair, but both could be carriers for the gene for red hair. If this was the case, perhaps one in four of children might have red hair. If one of the parents has bright red hair, and therefore carries two of the changes (one on each of their chromosomes), and the other parent is a carrier, then perhaps 50% of the children might have red hair. It is this aspect of genetics, and the mode of inheritance, that explains why hair colour might skip generations.

There are different sorts of red hair. Some people seem to have what we call “strawberry blonde”, some bright red and some auburn. As far as we know, the genetics underlying these differences are fairly similar, in that changes in the gene referred to above, seem to be important for all sorts of red hair. However, if you have bright red hair it seems you are much more likely to carry two different copies of the gene than if you are a strawberry blonde. We are, however, not completely certain about some of the details in this particular aspect of the work.

There are some other puzzles about red hair. Some men might have red beards but dark coloured hair. This is not entirely surprising as in many mammals the front of the body is a slightly different colour to the back. In some animals, the molecular basis of this is clearly understood, as in these animals, they produce a different protein that seems to have the opposite effects to the red hair gene mentioned above. In man, we don’t think this is the case, but we also observed that people who do have red beards are more likely to carry at least one different copy of the red hair gene.

Another puzzle is why hair colour changes so much during life. Most people are aware that hair colour tends to be lighter at birth and gets darker, particularly during adolescence and puberty. Apart from saying that the cells that produce melanin become more active at this period we don’t understand why this is. Similarly, of course, we don’t really understand greying and lightening of the hair in old age. People with red hair often have different coloured hair at different times of their life. It seems that it is more likely to be red in childhood or in early adult life, than in later life.

One medical importance of red hair is that individuals with red hair are, on average, more likely to burn in the sun and they are at an increased risk of skin cancer. The sensible advice seems to remain that since it is painful and uncomfortable to burn repeatedly in the sun, it is sensible to alter your behaviour such that you don’t suffer the discomfort! On the other hand the risks of skin cancer should also be put in context. For instance if you have red hair, the medical risks don’t compare with the far greater and much more serious risks from smoking and drinking large amounts of alcohol or being very grossly overweight.

We don’t know with certainty when the first “red heads” walked the earth but, based on our own research, our guess is around fifty thousand years ago. In evolutionary terms, this is relatively recent, and although we can’t be certain, the explanations for the development of red hair generally fall into two groups. The first, is that there may have been some advantage to having red hair and pale skin. One reason for this is that you make vitamin D in your skin, and therefore you are less likely to get rickets (vitamin D protects you against rickets) if you have pale skin and there is not much sunlight around. An alternative explanation, which some of our own work supports, is that it may have just been due to chance in that, to state it simply, nature may have been fairly indifferent to hair colour in areas of the earth without high sunshine. Diversity may rule! >

Red Hair Genetics

 

[CharleyH]

With absolutely no scientific (biological or anthropological) evidence to back this up I would say that red hair can show up in any generation without reference to genes; a hair colour descendancy.

Assuming that hair colour is a function or result of geographical location (as skin tone) then we see that it is indeed true that Scotsmen have red hair, Scandinavians are blond(e) and Africans have black hair.

These are evolutionary changes (yes I know that genes are the means of evolution) and you can conclude that the potential for red hair is inherent in all genes irrespective of genealogy.

Gauche

HA! I love it!

Personally, I have two cousins (from the same parents) who have red hair. One parent is blond, the other dark, and there are no other 'red heads' in the family.

AND don't be tempted into the obvious cliche' .

 

[Sarastro]

Some idle speculation: I have long been under the impression that red hair comes into being via the genetic clash of dark hair and blond hair. Still sounds pretty plausible to me after having read the above. These kinds of melanin are mixed, retaining elements of both. Evolutionarily, that would mean that red hair comes from the first time a population of blond-haired people mixed with a population of dark-haired people. Since the number of people in prehistoric times were minute compared to modern numbers, there were almost certainly various geographically isolated populations that evolved different traits. Of course, it's difficult to be sure that there were ever a 100% blond population, but there are areas of Norway and Sweden where 80% of the population is blond. Backtracking, it seems logical that they are descended from a purely blond population that once lived isolated from dark-haired peoples.

Of course, it's not as simple as: 1 blond + 1 darkhair = 1 redhair (although this is not unheard of - as a kid I lived next door to an expatriated British family. Blond mother, dark-haired father, three red-haired kids!) - the genes commonly get mixed over many generations.

But, this reasoning may only be valid if one looks at dark and blond hair as opposite ends of the hair color scale (also genetically), with "pure" forms at each end of the spectrum. This, of course, may not be the case at all. Maybe European populations just produced some lighter-haired individuals here and there, and there was never a purely blond population anywhere. Even so, I think the "clashing of the dark and blond hair" scenario for the origin of red hair still works, as dark and blond hair seem different enough to produce a new variant of hair color when they clash genetically.

Just my two cents!

 

[gauchecritic]

That was my first thought too Sor, black to white with the middle colour being red, unfortunately for that theory, everyone in the whole world has the same ancestry, which is African.

Gauche

 

[minsue]

My observations of recessive genes

I've given up trying to figure out recessive genes. Everyone in my family has blue eyes, but mine are green. (It took my mother about 16 years to admit to herself that they aren't blue)

My brother and his wife have two children together and one child from her previous marriage and both my brother and his wife have thick, brown hair. My niece from my sister-in-law's first marriage looks just like her: Brown hair that's fairly thick and skin that tans easily. My other niece looks, oddly enough, just like me: Fine, limp blonde hair and pale skin that burns within 20 min. My nephew looks like my father: light strawberry blond hair and that same pale skin.

The person with oddest combination of dominant/recessive genes I've ever known was a high school boyfriend. His mother had the coloration commonly referred to (at least around here) as 'Black Irish' and his father's background was Mexican. His sisters looked slightly different from each other in that, while both had brown hair, one was pale and the other tan. He was tan, but also had red hair. Truly a fascinating look.

- Mindy, babbling on as usual

 

[thenry]

As a budding geneticist…

give up on understanding red hair and green eyes and why they associate. It's as if you take your little Mendelian square with Big B's for Brown and little b's for blond.

BB=Brown
bb=blond
Bb, bB=Brown

and then somewhere on the far side of the room is a different square entirely with about ten settings for "redness." Depending on what's in the first square and which of the "redness" settings you have, you get a hair color. The reason it seems to run in families only sometimes is that it requires the preservation of two "settings" instead of just one, like blond and brown.

 

[SummerMorning]

As far as I know - Sor - blonde hair is also recessive. Put simply - dark hair is the original human hair. All the other colors are just variations (or peroxide ).

Blonde hair originated due to a mutation somewhere in the Eastern Baltic - around Estonia, Latvia and Lithuania. You get almost concentric circles of blonde hair and blue eyes radiating out from there. Essentially, the further from this region you go the lower percentage of blondes in the European population (on average). America doesn't count, since it was settled later and faster...

This just goes to show that peoples didn't move around as much as guys with swords who lorded it over the peasants.

 

[SummerMorning]

BTW - my hair is blonde, really...

 

[dr_mabeuse]

thenry is right. While the various amounts of melanin might blend to give various colors, the genes for the melanin themselves are discrete quantum units. You either have it or you don't. There's no in-between

By the other reasoning, I guess we could say that if a blond crosses with a bruntette the babies will be born with gray hair, while it's well known that when babies are born it's the parents' hair that turns gray.

---dr.M.

 

[oggbashan]

One of my cousins who shared his bright red hair with his brothers and both parents met a girl at a dance who had the same shade of hair.

They got talking and now they have three red-headed children.

Is that 'natural selection'?

Og (who had a reddish beard, was blonde, then mouse and is now grey)

 

[snooper]

Thanks for all the repies. The Edinburgh University reference is most interesting.

The question arose in a book I am writing and you have all helped a lot.

 

[Sarastro]

OK, lots of comments here...

Gauche said:
>That was my first thought too Sor, black to white with the middle colour being
>red, unfortunately for that theory, everyone in the whole world has the same
>ancestry, which is African.

Yes, but the reasoning goes: Black (African/south European) to brown (central European) to blond (north European), and then blond doubling back to mix with (often south or central European) black/darkbrown, creating a new combo (unless the dark parent is very dominant, as Africans would be - although I have actually heard of red-haired North Africans, and seen one on TV). When dark and blond genes mix, it seems logical that there will be a wider range of colors genetically available for the off-spring to "choose" from, certainly incl. the combination that results in red hair. So red hair would result in 10 or 20% of the cases, if the parental color dominances were relatively matched.

OTOH, the Viking settlement on Sicily should then have created a bunch of red-haired Italians, which doesn't seem to be the case... There *are* a few blond Italians (Terence Hill, for one), but most of them (and blue-eyed Italians, too) are from northern Italy.

By the way, *is* there really any real statistical above-average occurrence of red hair in Scotland, or is this a myth?? I know the U.K. in general (incl. Ireland and Wales) do have many redheads (many of whom are freckled), but we also have them in northern Europe (my half-brother is ash blond with red beard, as is his uncle).

SummerMorning said:
>As far as I know - Sor - blonde hair is also recessive.

(Sor?! Who is this Sor?)

Generally, yes, but not entirely. If you are a white person with a vast majority of blond ancestors, you are also quite likely to have blond children, even with a dark-haired (European) person. (It's different if the other parent is Asian or African, whose dark hair and eyes are extremely dominant.)

I know a couple of sisters, where one has blue eyes, freckles and platinum blond hair, and the other has near-black hair and brown eyes. They have the same parents, one being dark and one being light, so one sister takes after one parent, and the other after the other. Since this is in northern Europe, I'd call the blondness about as dominant as the "brunetteness".

Genetic dominance and recession are not limited to the immediate parents; its a mix and a jigsaw of everyone in your entire genetic history, although the traits from the last couple of generations often tend to be strongest.

Then there are Australian aborigines, who actually also have a form of blond hair. It is kind of beige, and a different form of melanin than European blondness. I'm not sure just how common it is, but it also does occur in aborigine children. I saw a pic of a blond aborigine boy in an anthropology book once, and AFAIR it said in the book that it was even a dominant trait! It's probably limited to certain populations, though. If there are even any left by now...

>Blonde hair originated due to a mutation somewhere in the Eastern Baltic
>- around Estonia, Latvia and Lithuania. You get almost concentric circles of
>blonde hair and blue eyes radiating out from there. Essentially, the further
>from this region you go the lower percentage of blondes in the European
>population (on average).

Do you have a source for this?

>America doesn't count, since it was settled later and faster...

And Australia... I've often wondered just what the blond percentage of the population in the U.S. and Australia are. The Aussies, judging by their television, seem to be virtually every bit as blond as northern Europeans in general, but America is more of a melting pot (and probably use more bleaching). Even so, blondness seems to be very, very common in the U.S., too...

We can then go on debating whether blondes are sexier than brunettes, and if there's a sexual selection favoring blondes in progress... I'm tending to think there is!

I have to admit blondes are sexy (and evolutionarily, I hear it's because a light complexion makes a person more likely to exhibit their diseases if they have any, meaning that a healthy blonde is more likely to have good genes than a healthy-looking brunette, who might have invisible health problems...), but I have always preferred brunettes, tending to (perhaps unfairly) think them more intelligent. Ultimately, I expect my attraction to darkbrown hair and brown eyes owe to the fact that those are my mother's (and my own) colors, meaning that I've been conditioned to like them since infancy, really. This goes well with a science encyclopedia I have, which says that, statistically, people have a tendency to marry people that resemble themselves.

 

[Madame Manga]

I love this sort of subject. Human diversity! Those little things that make us individuals, no two exactly alike. Fascinating.

Red hair in particular is near and dear: my husband is a redhead and maintains that all redheads form a higher order of some kind, sort of like the Red-Headed League. His coloring comes from Norwegian genes, and as I understand it, Northern European redheads ultimately trace to the Viking conquests of a thousand years back and their assimilation into the local populations. So the red-headedness of the Irish is ultimately Scandinavian rather than Celtic.

Then again, I have a cousin-once-removed with that interesting combination of tan skin and dark red hair. His mother is biracial (African-American and white) and his father is blond. None of us would have predicted Jeff's coloring, but it's kind of cool, because his mother's adoptive parents are redheads!

MM

 

[snooper]

Red hair in particular is near and dear: my husband is a redhead

Out of curiosity is the hair on his face (beard or moustache) the same colour as the hair on his head? I seems that this is not always so, and rumour hath it that when they are different, the facial hair is darker.

 

[SummerMorning]

Sar...not Sor...Sar...

You mentioned the offspring of a blonde European and a dark-haired European - trick is that most dark-haired Europeans probably carry recessive blonde genes as well, so it's statistically more likely that their offspring will have lighter hair. But blonde hair (among Europeans) is allways recessive. If a blonde European (bb) has children with a black-haired European (BB) the children will always be black-haired...but most black-haired Europeans are Bb, rather than BB...and of course there are different types of Bs and bs, but the Bs beat the bs every time (and it gets confusing )

Of course, this does not take into account chimeras - essentially nearly every individual has cells that have all their chromosomes from just one parent, i.e. not mixed - so we're all far more patchwork than we'd like to believe. This is why you can get tortoise-shell cats for example. Now, most people don't have different colored patches of skin (though some do, and birth marks can be an example), but most people do have clusters of cells that are chimeric. And you could end up with a couple of locks of blonde hair when all the rest is black... (and I do actually know such a girl, she has dark brown hair and one lock of blonde hair - a patch of skin about 1cm square near her forehead).

 

[SummerMorning]

Out of curiosity is the hair on his face (beard or moustache) the same colour as the hair on his head? I seems that this is not always so, and rumour hath it that when they are different, the facial hair is darker.

It is not always so. Sometimes it's darker, sometimes it's lighter. Mine is darker. My brother's is lighter.

But then, the color of all hair is suspect. I used to have nearly black hair, yet recently people have been calling me blonde...it's the eyes, I think.

 

[philadelphus]

Hey, chimeras ... sounds pretty cool! A blonde lock on her forehead - that's like Rogue of the X-Men!!!

 

[thenry]

Yeah, chimeras are cool as long as it just involves hair or eye color, oddities of which usually have more to do with neural crest cells than mosaiicisms.

Chimeras are not so cool when the different bits don't show, like if it were your lungs, and the recessive trait was cycstic fibrosis instead of blond hair, or your liver and PKU, or your brain and Down's syndrome. On the other hand, no one knows how common chimeras are because most go undetected unless one of the mixes has a genetic problem. Some think that every person contains a percentage of autosomal mosaiicism.

A few months ago, a woman was having tests done on her children which revealed all three had the same father but one a different mother. Since maternity is one of the few things you *can* be sure of, they looked again and found that each of her ovaries had a different set of chromosomes, so each egg "looked" like it was coming from different people.