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? Mixed race inheritance through multiple generations

Genetics as it applies to evolution, molecular biology, and medical aspects.

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? Mixed race inheritance through multiple generations

Postby ulara » Thu Jan 25, 2007 5:54 am

We (family) have a debate going regarding the genetic passing on of mixed races. I have not been able to find any information regarding this.

Subjects are one female and one male who will be married and hopefully have children.

Female's father is of Black/White descent, (Black father, White mother-not sure about grandparents), and female's mother and grandparents are fully Hispanic.

Male is of European descent, father's parents and grandparents are Italian/Polish, mother's parents and grandparents are Irish/English.

I believe that the future heredity factors for any children born to this couple will be a mixture of the genes of all past generations.

The other side of the debate says that race genes will disappear after a couple of generations if not kept alive by reintroduction of those races into the gene pool. For instance, if a child of said couple who is now a mixture of predominately White, then Hispanic, then Black, marries a fully Black person, then their child marries a White person, this will cause the Hispanic genes to eventually disappear and no longer be a heredity factor.

I know genes can become recessive but aren't they always there even through several generations?

Thank you for any input.

Laura
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Postby Doc44 » Thu Jan 25, 2007 6:13 pm

You need to be a little clearer in your question.

Are you interested in all racial characteristics or are you only interested in skin pigmentation?

Percent of pigmentation is controlled by incomplete dominant alleles (genes). Each gene contributes differently to the percent of pigmentation expressed.

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Postby MrMistery » Thu Jan 25, 2007 7:19 pm

incomplete dominance? neah.. it's poligenic. 4 sets of alleles. Incomplete dominance is only between two alleles.
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Postby Doc44 » Thu Jan 25, 2007 8:37 pm

Yep....brain flatus.

Was thinking red X white = pink
duh.

Ususally AaBbCc X AaBbCc = multiple percentages of pigmentation, ranging from AABBCC to aabbcc with many different genotypes in between the two homozygous in the f1 generation.

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Postby MrMistery » Thu Jan 25, 2007 9:33 pm

here is a simplified view of inheritance of skin color, from campbell and reece
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Postby Doc44 » Thu Jan 25, 2007 11:36 pm

and sort of a shaded Square way to look at the ratios:


http://waynesword.palomar.edu/lmexer5.htm

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? Mixed race inheritance through multiple generations

Postby ulara » Sat Jan 27, 2007 8:26 am

Thank you all for your responses. I guess I made it too confusing with my long examples, or I'm so ignorant of basic biology that I can't explain it properly....sorry!

What we wanted to know is -

If different races are a part of a person's ancestry then future generations of offspring will have a genetic makeup of all of those races, correct? So if a person who has a lineage of almost all Japanese let's say, but has a great-great grandmother who was an Irish caucasion, wouldn't the genes from the one Irish caucasion become part of the genetic mix forever for future offspring?
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Postby umsikas » Sat Jan 27, 2007 8:03 pm

You are assuming that the Japanese-Irish person will have offspring in the first place. Keep in mind that both Japan and Ireland have very low birth rates today, at the rate of 1.86 and 1.40 per woman, respectively. (A rate of 2.1 is needed to sustain the same population).

http://en.wikipedia.org/wiki/List_of_co ... ility_rate

Those identified as "multiracial" tend to come from rich, cosmopolitan countries with low birth rates. There is no guarantee that they will "take over" the gene pool of the country in question.

Immigration patterns can also change over time. Asian immigration to the US is changing; richer Asian countries such as Japan, Korea, and Taiwan today are net importers of immigrants, i.e. more Japanese-American immigrants move to Japan than Japanese move to the USA. The future of the US will increasingly consist of Hispanic, Hindu, Muslim, or African stock; but world economic conditions may change again.

In some countries such as China, a mix of ethnicities led to the formation of new ethnic groups, such as the Han Chinese. In the US, we see a similar formation of a new "Hispanic" ethnicity.
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? Mixed race inheritance through multiple generations

Postby ulara » Sun Jan 28, 2007 4:17 pm

I thought my question was a very simple one but I guess not. This has nothing to do with race. I was using different races in my original post, as well as my followup, as examples. It it could be anything having to do with inherited GENES. It is a given that we are talking about offspring, so whether or not people have children doesn't have anything to do with it. I am simply trying to find out if inherited genes ever completely disappear or are always present in future generations.
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Postby MrMistery » Sun Jan 28, 2007 5:45 pm

The answer to your question refers to statistics as well as genetics

I am going to consider the trait of skin color, although the rules are the same for any race-specific characteristi. think of it like this. when great-grandma and great-grandpa have a child, if great-grandpa is irish and great-grandma is black then the child will probably be be somewhere in between(because of probabilistic arrangement of choromosomes in independent assortment). If this grandpa marries a grandma that is white, their child will probably be somewhere in between the parents, so a little blacker than a white person, but close. This parent marries a white woman again. Their son will be almost or totally white. Each time it depends on wether you get the gene from one parent or the other. So, if there was one great-grandma that was black and everyone else in the family since was white, then after 5-6 generations it is extremely probable that all the offspring will be white and there is no trace of the orginal black grandma.

Now let's think about a more pragmatic example. A race is not only about skin color, but many other characteristics. Due to the laws of probabilities with large numbers, the original son of the caucasian man and black woman will probably have most of the traits in between the two(most complex racial traits are indeed poligenic). As more and more genes of caucasian people enter the family gene pool, the black great-grandma's genes will slowly dissapear, and after 5-10 generations all traces of her will most likely dissapear.

So to answer your question: yes, inherited genes usually dissapear after many generations, although it is possible for them to remain. It is a matter of chance.
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Postby q-she » Sun Jan 28, 2007 6:05 pm

that`s right. cause i whatched a film called "rabbit proof fence" the films deals with this topic. there are whites mixed with aboriginels. after some generations, just after two or three i think, you can not make out a difference between the original whits, and the whites once mixed with aboriginels.
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? Mixed race inheritance through multiple generations

Postby ulara » Mon Jan 29, 2007 3:06 am

Thank you MrMistery for the excellent explanation, and for clearing that up for me!
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