Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: babygyrl0221 on 08/01/2004 01:55:55
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My boyfriend and I aare having a major argument. He says it is genetically IMPOSSIBLE for a person to have both brown hair and blue eyes. I completely disagree. I even had an example: actor Elijah Wood
Could someone please clear this up for me. email me babygyrl0221@yahoo.com
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I'll say this is denfinetely possible as the colour of eyes and hair are not determined by a single set of alleles so the characteristic is polygenic. And I don't think the alleles are located on the same chromosome so they shouldn't influence one another. However I'm not a genetic expert so cannot give you the correct answer. Quantum is quite good at this. And there's also genegenie.
Angel
"The people who will succeed are those who see the invisible and do the impossible."
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I thought you've just done this topic a couple of weeks ago.
Tom
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I have a neice with brown hair and very beautiful blue eyes. So there.
Welcome to the forum!
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John
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quote:
Originally posted by nilmot
I thought you've just done this topic a couple of weeks ago.
Tom
Yes. I've just done the topic but the genetic we learn in A level is an over-simplified version. We assume characteristic such as eye colour is controlled by a single set of alleles.
Angel
"The people who will succeed are those who see the invisible and do the impossible."
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Its actually quite common in Ireland to have dark and sometimes black hair but blue eyes and pale skin aswell.
There are also quite a few people in Ireland with dark hair, blue eyes and dark, continental looking skin. I heard that its because some Spanish were shipwrecked off the Irish coast on their way to fight the English at the Armada in the 16th century. They then settled. However it is still a myth and as far as I know has never been investigated scientifically. They are known as the 'Black Irish'.
"Crushing truths perish by being acknowledged." Albert Camus
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I don't know anything about the genetics of eye and hair colour, except that they're complex and rely on interplaying genes. If he says it's genetically impossible, he must know a lot about the genetics of eye and hair colour? You disaggree from your experience. Why not ask his why it is impossible, and if he can't tell you then he'll have to conclude that it is indeed possible.
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Well we know its not impossible QC otherwise several thousand Irish people wouldn't exist. Its a celtic trait - hence its also found in scotland. Being half Irish, I got the pale skin and almost black hair, but inherited brown eyes from my english side.
It looks like you have already posed the question - why is it impossible? I'd be interested to know what babygyrl0221's boyfriend's theory is, if he has one!
"Crushing truths perish by being acknowledged." Albert Camus
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The vast majority of irish people have either brown or black hair, don't be fooled by dodgy "oirish" films made in america where we all run about saying "bejaysus" and all got red hair. Only about 4% of irish people got red hair. The vast majority of Irish people are blue eyed (about 85%) and Type O blood. Now if your boyfriend was correct then how does he explain the fact that majority of irish people are both dark haired and blue eyed.
Claire is right it's somewhat of a "celtic" thing. Well given recent studies showing very close genetic links between irish, welsh and basque some have said that we are renemants of neolithic population of europe.
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Eye colour is thought to be a polygenic trait (many genes), although it's not 100% clear as some eye colours (brown & blue/green) have shown single gene inheritance in family studies. Hair colour is considered a complex trait as factors influencing colour include the type of melanin, how much/how packed into the hair etc. I'm not sure of the reasoning behind your boyfriends theory, and I'd be curious to know, but I reckon you're the winner! [:D]
BTW, I have brown hair and blue eyes, as do my brothers.
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Some info I picked up regarding this topic in genetics class this week:
Eye and hair color genes are on the same chromosome in humans. Therefore, they are closely linked as any gametes produced will always have the same eye color genes with the same hair color genes. There are multiple genes for these and some cases of incomplete dominance, but it's all on the same chromosome. This is why the two are so closely linked in many cultures.
However, there's a phenomenon in the Prophase I stage of meiosis where homologous chromosomes (remember you have 23 homologous pairs, for 46 total) will "cross over" or exchange a portion of their genetic data. In this way, you can separate the hair/eye color genes from your father from each other and be able to have Mommy's hair but Daddy's eyes. This is one of the things that allows for greater genetic variation.
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Actually I don't believe that all the genes for human eye and hair colour have been mapped. I understand that genes coding for brown eye colour (BEY2) and brown hair colour (HCL3) have been assigned to chromosome 15q (from linkage studies), while the MC1R (melanocortin 1 receptor) gene, which is also considered to be involved in hair/eye pigmentation is on 16q. Another gene, the Agouti Signaling Protein (ASP)on ch. 20 has also been implicated. It's been postulated that there are many more genes involved as well. Cannabinoid, I don't believe that your genetics lecturer has given you completely accurate information, because the complete picture is still unknown.
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I have brown hair and blue eyes. I think being multiracial can make people appearence's look distinct. I have like 16 races in me, but im made mostly Scandinavian, and German. Yet i do share large precentages of other races as wellm like British and italian. I just see this geneology as nature. Like animals, if you crossbreed two or more different purebreeds to get a a new breed, of course the breed is going to look like a mix. Typically we see this in dogs, but you see it in other animals as well. So "mutts" are referred to multiracial people.
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I have brown hair and blue eyes. I think being multiracial can make people appearence's look distinct. I have like 16 races in me, but im made mostly Scandinavian, and German. Yet i do share large precentages of other races as wellm like British and italian. I just see this geneology as nature. Like animals, if you crossbreed two or more different purebreeds to get a a new breed, of course the breed is going to look like a mix. Typically we see this in dogs, but you see it in other animals as well. So "mutts" are referred to multiracial people.
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When I was younger, I had dark curly hair and blue eyes, just like my dad. Later on, about from when I was 12 or so, my hair became straighter (though it still curls after being washed or going to the pool) and lighter, and my eyes are turning green (sort of aqua colour right now) exactly like my mother ... she has slightly curly hair sometimes (not all the time) and her eyes are emerald green. What would explain this? I know lots of babies have blue eyes when they're born, but they change to their real colour in a year or two. Mine stayed blue until I was about 12. All my dad's family is from south america, my mother's mother's family from australia and my mother's father's family from scotland.
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gene: I think those other genes you're mentioning are involved in an epistasis scenario that can affect the expression of eye/hair color, but the genotype for your hair and eye color are located on the same homologous pair. Genotype doesn't necessarily determine how the trait is expressed, as you well know.
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Yep, I agree cannabinoid, but I'm not convinced that the loci for hair and eye colour have been accurately determined.
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I have black hair and very blue eyes,my ancestry is italian,english,spanish and possibly there is chinese and irish on my fathers side.....so i think i got my hair and eye combination from that mixture.....my parents both have very dark hair,Dad has grey blueish(with a brown ring around the pupil) eyes,Mum has dark brown.
I also once had a friend from India who had dark hair and blue eyes and i have heard there are a lot of people in parts of pakistan with blue eyes and black hair.
So dark hair and blue eyes are definitely possible
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Found some more info:- Genes for brown and blue eye colour, called Bey1 and Bey2 are found on chromosome 15; a gene for green and blue eye colour, called Gey1, is found on chromosome 19. There are likely to be several other (unidentified) genes controlling eye colour. Two genes for hair colour are very close to these eye colour genes. There are at least two genes that control brown hair colour, HCL1 on chromosome 19 and HCL3 on chromosome 15. Each of these is very close to the corresponding eye colour gene on each chromosome, therefore usually inherited together (due to linkage). It is not yet known what these genes make, or how they produce eye/hair colours. There are various other genes involved in regulation of these genes, such as MC1R, which controls the cells that produce the various types of melanin. Eye colours including grey and hazel are not yet explained.
Obviously the gene model used above explains only a portion of human eye colour inheritance, but the linkage scenario (explained by cannabinoid) involving currently known hair/eye colour genes shows that inheritence of both the brown hair and blue eye alleles together is quite possible.
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Grey would be dillution of blue, and hazel a combination of brown and green, right?
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Something strange I've been wondering about. My eyes have always been blue, except when the mercury poisoning got bad. They turned grey. Now that I'm healthy they are blue again. What's up with that?
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I have blue eyes and brown hair , as does my son and two daughters and wifey too !!
'Men are the same as women...just inside out !'
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Gene: I don't doubt that there are more than one gene on other chromosomes that can affect the expression of eye and hair color, similar to the gene for melanin expression in labs. They have a gene for either brown or black coat color (don't remember which is dominant) but they have another gene that allows for melanin expression. If that genotype is homozygous recessive, they do not create enough melanin and black labs become brown and brown labs become yellow.
A similar situation could certainly arise in eye color for humans....your eye color gets set at either blue or brown, then another gene controls the creation of the protein that makes up the pigment and can influence the expression of the eye color. (i.e. brown becomes hazel, blue becomes grey, and so on) It's certainly more complex than I explained because there are more than 2 alelles for eye color.
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My question now is, did you win the argument babygyrl0221????
Science is organized knowledge. Wisdom is organized life.
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I have very dark brown curly hair and deep blue eyes. My hair was completely straight until my early teenage years. My dad is tall, blonde and blue eyed and my mum is short with very dark wavy hair and brown eyes. My mums family name is McGhee and I think there is an irish connection.
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Yes, there most definitely is an Irish/Celtic connection.I have very dark brown hair and blue eyes and very pale skin.My Father's family are Irish and my Mother's Welsh.My Father and Mother both have blue/green eyes, though my Fathers hair was originally red/brown and my Mother's mousy brown so there you have it!
I have always been told about a Spanish connection somewhere in our roots on my Dads side so what has been posted already about that I would agree with.
I personally love being a bit different with my weird colouring!
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i'm 100 percent scottish i have dark brown hair and blue eyes and freckles which i've always had a dermo doctor tried to tell me i was out in the sun to much hhaaa lollol
i said ok on the the west coast of scotland haaaaaa
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Hi man,
We know one think eye is a must important site in our body. The structure of your face helps protect your eyes from injury. Still, injuries can damage your eye, sometimes severely enough that you could lose your vision. Most eye injuries are preventable. If you play sports or work in certain jobs, you may need protection.
The most common type of injury happens when something irritates the outer surface of your eye. Certain jobs such as industrial jobs or hobbies such as carpentry make this type of injury more likely. It's also more likely if you wear contact lenses.
Chemicals or heat can burn your eyes. With chemicals, the pain may cause you to close your eyes. This traps the irritant next to the eye and may cause more damage. You should wash out your eye right away while you wait for medical help.
Thank you.
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Next time you post a spammy link you might wanna make sure that it works first!!
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Good job Luke.. History now.. thanks!