Genetics regarding biracial people?

[Esther]

I have a question, it may be a stupid one, but I don't understand. I know several people who are half black and half white, and come out looking pale ( not lightly tanned, or yellow-ish), with or without freckles, blue/light or dark eyes, and they look white, southern european, and sometimes even north european. Let's say their parent who is 'black', is 80-90% african, does this mean that the child, is 30-40% african as well? Or that the child only inherited the european genes? I never understood this, and I thought it fits this subject a little, okay not really, but should I make it a new thread instead then? Thanks!

And if they inherited mostly the european genes, could they still be 30-40% african? As in someone looking like adriana de lima, but still being up to 40% 'black'?

I'm sorry I'm new at this, so sorry if the questions seem dumb

[rapunzels tower]

This girl is an example of what you mean;

http://sphotos.ak.fbcdn.net/hphotos-ak-ash1/hs549.ash1/32073_1292266711440_1373436586_30627172_5445434_n. jpg

Her mother looks slightly mixed but could easily be a continental West African.

[Esther]

Stupid title, sorry typed it out quickly -.-

---------- Post added 2010-09-13 at 22:10 ----------

Yes that is close. But I know a girl, whose father is black and she is literally pale, green eyes, curly dark hair, and her features are euripoid as well :-s The only thing exotic about her are her lips and hair ( not kinky curly btw) And she's not the only example. I wonder if in cases like these the percentage of african is slightly less, or that she could still have about to 30-40% african genes, despite her phenotype.[COLOR="Silver"][COLOR="Silver"]

[Esther]

anyone?

[Vrijheid]

Mixed-race people are unquestionable healthier and more intelligent. The ladies love genetic diversity, and Africa is the most diverse continent on earth, which speaks for itself why the white ladies love the black man.

[Zwaan]

To answer your question, no a child cannot inherit only the European genes. I think the biracial people you are thinking of, are the one's whose "black" parent is a "New World Black", correct?

I'll try to explain as clearly as possible.

A child will always inherit roughly 50% of each parent. (The possible decimal variatian depends on the gender ue to the XX chromosome being longer than the XY). If you have a 100% Sub Saharan African parent and a 100% North European parent, you will get a 50% Sub Saharan African and 50% Northern European child.

Now, a lot of these so-called New World blacks have European admixutre to varying degrees. African-Americans are said to have on average 20% European admixture, though many have less and several have more (sometimes easily having over 60% European blood). Now say you take an African American parent, with average admixture, he will be 20% European and 80% African. Say they have a child with a 100% European parent. Again, since the child always gets 50% from each parent, the child will get 50% European blood from the European parent, but will now get only 40% African blood from the African American parent and an extra 10% European.
Put it all together and tada! You get a child that is 60% European and 40% African.

As for pigment, hair colour, eye colour and skin tones are all regimented by different genes, as well as melanin levels and environment of course (as well as nutrition!). In women, fertility levels will also affect skin tone.

What you need to understand about genetics is that there are dominant and recessive genes. A dominant gene will as a rule express itself no matter what, be it heterozygous (that is oly one copy of the gene) or homozygous (two copies of the gene). Recessive genes only express themselves when they are homozygous. When a genotype (set of genes) is heterozygous, although the dominant gene will be the only one to appear (as a rule) the recessive gene is still there "hiding" (sometimes it will slightly express itself in a variety of ways).

As generic as it is, for the sake of simplicity I'll take the example of blonde hair and blue eyes, with brown hair and brown eyes. The chart will go as follows:
Brown eyes: B
Blue eyes: b
Brown hair: Br
Blond hair: bl
The capital letters mean the gene is dominant.

So again lets start with a 100% Sub Saharan African parent. Their genotype is BrBr BB. Now lets take a 100% European parent, their genotype is blbl bb. Since the child inherits 50% and one copy of each gene from each parent the child with be 50% SSA, 50% Euro with a genotype like this: Brbl Bb. Since brown is dominate in both hair and eyes, the child will appear as brown haired and brown eyed. Sometimes the shades of brown can be lighter due to the recessive genes, but at times it is just ranom natural variation and one shouldn't look in to it too much. We will call this mulatto/biracial child, Child A.

Now seeing as Child A has one copy of each gene he is heterozygous for both his hair and eyes, meaning he has a 50% chance of passing on either copy of his genes. If child A decides to have children with a blonde-haired, blue-eyed person, whose genotype is blbl bb this is what will happen:
Brbl Bb + blbl bb
The child will invariably get one copy of the blonde hair gene from the second parent as well as one copy of the blue eye gene.
= bl? b?
Since Child A posseses one copy of each brown blode and blue there is a 50% chance of passing on either copy.
The possible resulting combinations are
= Brbl Bb (like child A)
= Brbl bb
= blbl Bb
= blbl bb
The odds are in favour of the recessive genes, but odds are odds and genetics is still a "lottery". But basically it means that the resulting child who is 25% African and 75% European has a 50% chance of having blue eyes, 50% chance of having blonde hair and a 25% chance of having both.

If Child A however decided to have children with a person whose genotype was the same as theirs:
Brbl Bb + Brbl Bb
= BrBr BB in this case the light hair and light eyes genes are completely erased from the resulting offspring's genetics. But this is only a 12.5% chance of happening.
= blbl bb this time the dark hair and dark eyes genes are completely gone. The child will express the blonde hair and blue eyes. Again only 12.5% chance of happening.
= Brbl BB in this case the light eyes genes are completely erased but the light hair gene remains hidden. 25% Chance of happening.
= blbl Bb 25% chance of happening, blonde hair and heterozygous brown eyes.
= BrBr bb 12.5% chance of happening, homozygous Brown hair and homozygous blue eyes
= blbl BB 12.5 % chance of happening. Blonde hair and brown eyes.
= Brbl Bb same genotype as each parent, 50% chance of happening.

And last but not least if Child A goes with a person whose genotype is BrBr BB it will result in the possible outcomes of
Brbl Bb + BrBr BB
= BrBr BB the light hair and light eyes has disappeared from the genotype, this has a 25% chance of happening
= Brbl BB light hair is hidden, light eyes are gone, this has a 50% chance of happening
= Brbl Bb same genotype as Child A... Light hair and light eyes still present but being recessive are not expressed. 50% chance of happening.
= BrBr Bb, light haire gone, light eyes hiding, 25% chance of happening.

The last example is probably what the genotype of most New World Blacks vary in. That and maybe the second example. So you see it is very possible for the genes for light eyes and hair to remain unexpressed but still transmit own several generations. All it needs is to be matched up with an other set of recessive genes, to express itself. This is why its even possible to find so called New Worl Blacks with blue or green eyes. And this is why New World Blacks who have children with a light-haired, light-eyed European have fairly good odds to have children with either light hair or light eyes or even both.

For the skin it relys on various factors, there is the genotype of course which when heterozygous expresses itself as medium brown as a general rule, but there are several other genes that factor in to it that don't always correlate with race. Then there is latitude and sun exposure, gender, and as I stated, fertility in females.

Hope this cleared things up for you.

[JackKnightstick]

Zwaan summed it up quite clearly, I guess she was talking about people like this...

Quincy Jones and his daughter.

http://gliving.com/wp-content/uploads/2008/03/rashida-jones-fashion.jpg

I'm a perfect example...23&me says I'm only 60% African, I believe that is false, I think I'm more like 85% West African/Southwest African in ancestry. My fiancee is 100% Euro from Central Europe.

So our kids would be

42.5% SubSahara African, 57.5% Euro (specially about 36.25% Northern Euro, 21.25% Southern Euro) (all based on DNA test we both took)...

So our kids can look like a lot of stuff depending on the mix of recessive and dominant genes they get from us.

Last time I was in Switzerland, i saw a boy who had a blond afro and green eyes, his mother was obviously straight from SubSahara Africa, his father was Swiss...the kid was about 2 years old...you can see all types of mixes.

I have a cousin who has a white father, she has green eyes and black hair, her sister has dark brown (black) eyes and black hair, but sister with the dark eyes has a facial structure that is more Euro, while the "lighter one" has a more African face structure. LOL

I also think that genetic variation in Africans plays a role as well, not all African mixes with Euros look similar on average...

[Zwaan]

Yeah genetic variation in Africans AND Europeans actually. For example I noticed Northern Europeans (by this I mean the utost North-central and North-eastern line of France, The Netherlands, Northern line of Germany and all of Scandinavia excluding Finland) and Russians specifically tend to often dominate mixes in at least one way. On average I'd say they dominate the bone structure and skin pigment. Other features that are mostly flesh-based like the muscle and flesh parts of the face (nose, cheeks, lips etc.) tend to be mixed or tossed up a random in terms of what side dominates which part. For the rest of the body, its generally balanced between the two sometimes pulling to one side or the other etc. Depends on which parent has the most strong/extreme dominant traits and which one has more reduced traits. and on many other factors. Human variation!

[ethioboy]

I have a question, it may be a stupid one, but I don't understand. I know several people who are half black and half white, and come out looking pale ( not lightly tanned, or yellow-ish), with or without freckles, blue/light or dark eyes, and they look white, southern european, and sometimes even north european. Let's say their parent who is 'black', is 80-90% african, does this mean that the child, is 30-40% african as well? Or that the child only inherited the european genes? I never understood this, and I thought it fits this subject a little, okay not really, but should I make it a new thread instead then? Thanks!

And if they inherited mostly the european genes, could they still be 30-40% african? As in someone looking like adriana de lima, but still being up to 40% 'black'?

I'm sorry I'm new at this, so sorry if the questions seem dumb

Genetic recombination is random. This is the first fact you should know.


2) Ideally a person inherits ~50% of their mother's and father's meta ethnicity. Whether it be european or sub saharan african.

In the case of african americans who consider themselves black yet have varying degrees of admixture with europeans in their own population, it is possible for a 'bi racial' person who is half african american and half european american to be predominantly european american because his african american side is not purely sub saharan african.

Again because of the fact that gene inheritence and genetic recombination is random, the percentage inherited can vary considerably (though usually its close to the ideal).


An example of this. Person A thinks he is 1/16th German which means 6.25% German. however, in reality, he could be anywhere from 0-15% German because of the randomness of recombination. His parent could have recieved a disproportionately higher amount of German ancestry than 1/8th and therefore the offspring, which is Person A would have recieved more German ancestry as well.



Also there is no way for a biracial to just inherit european genes since the african american parent would still have a high amount of sub saharan african ancestry which will be present in the offspring.

I think what you are talking about is phenotype in other words the person looks white or European but that is because the Genes that control how a person looks or their phenotype are inherited from the european side of either parent instead of the african side or a mix of the african side and the european side.

[Aino]

Zwaan already wrote a very good description about how hair and eye colour is inherited. I wanted to add that the genes that determine your pigmentation and other racial features make up only a very tiny part of your genome. In other words, you can have a lot of African DNA but look European because you happened to inherit only the type of African DNA segments that don't affect how you look.

What combination of alleles you inherit from your parents is completely random. Let's say we have two persons who both have 40% African and 60% European DNA. One can look straight out of Africa, while the other may look predominantly European. However, both still have an equal amount of African DNA. It is just that by chance one of them inherited alleles that make him or her look African, while the other inherited the European versions of those alleles.