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erikaziger's avatar

Are there benefits to having greater genetic differences between parents?

Asked by erikaziger (345points) November 9th, 2010

Beyond the problems of inbreeding (e.g. marrying a cousin, sister) is it beneficial to offspring for parents to be highly genetically dissimilar? For instance it might lead to offspring with immunities to more diseases.

I also heard somewhere that if a couple has multiple children that have strong resemblance to each other this is a sign that the parents are very genetically similar. Conversely, I heard that if siblings of the same parents do not look alike this is a sign that there was a wide genetic variation in the parents (i.e. lots of traits to choose from). Is this true?

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4 Answers

Winters's avatar

I don’t know about the second part (my mother is Korean and my Dad is predominately Scots-Irish and my brothers and I all look the same), but as for immunity, yeah that is kind of true, but a big thing is that the child is also more unlikely to have any deformities, or any defect arising from a genetic origin.

Joybird's avatar

We breed for immunological differences. That is what is occuring when someone says the “chemistry” is phenomenal. The male only picks up pheromonal cues for fertility and ovulation BUT the female is able to read a whole host of information from pheromones and she zeros in on immunological differences choosing the male with the most different immune system that she has access to. Differences in immunological system may not have anything to do with similarity in looks or offspring however. THAT is another aspect of mate selection. People are generally attracted to people who have facial similarity to themselves and their families of origin. Don’t believe me…look at the engagement pages closely. couples have the same shape eyes, mouths, heads, and they have the same smiles..same placement of features on the face, same shape faces…elongated, heartshaped, round, etc. We also find symmetry to be more appealing. So it should come as no surprise that is we are choosing the person who looks the most similar to us and who has the most symmetry while having the most different immunological system that our kids will look like us and like each other.

JLeslie's avatar

The basic of genetics is you get one half of your moms DNA and one have of your dads. Many things only express themselves (we can tell you have the gene from the outside) if a person is homozygous for it. What that means is both parents give that same gene. If you are heterozygous, only from one parent, it may not be a problem. For instance, I think Cystic Fibrosis works this way. You can have two parents who are healthy, but if they both are heterzygous for CF and give that half of their DNA to the new embryo, and the embryo is homozygous, it will be sick. It is a recessive trait that only makes someone sick if there is not a domininant trait, normal gene, to balance it. The parents may have no idea they carry the gene, unless they are tested. Red hair is recessive. If both parents have red hair, all children will have red hair, because both parents have the recessive trait red on both sides of the DNA. If one patent had brown hair, but recessive for red, there is a chance of children with red or brown, if there is a paremt who is brown, brown, from both of his parents, the child won’t get her mommies bright red hair, because the father will only giving the dominant brown to the baby.

Ok, so back to your question. Just because children look like each other, does not mean other genetic traits are perfectly similar in both children. Red hair is a different part of the genetic code than susceptinility to breast cancer for instance. Although, there is a theory, maybe it is a fact now, that certain parts of the gene strand might move together as genes move in the beginning process of splitting to form an egg or sperm, meaning they might see more breast cancer in red heads (that is completely made up as an example).

Some ethnic backgrounds carry certain genetic diseases more often, so if part of the reason the parents and children and maybe the whole extended family look similar, it could be they come from the same part of the world, and so carry very similar traits and genetic diseases. Ashkenazi Jews get tay sachs more often, people from the Medeterranian we see thalessemia and intrinsic difficiencies, etc.

To sum up people who both have recessive traits for bad diseases, may have no idea they carry the disease, family members have a higher chance of having similar genes, and so when they make a baby, like a brother and sister, or first cousin, they are more likely to have a baby that gets the bad thing from both parents and actually be sick from it. But statistically it is actualky only a slightly higher chance than the averge population, it is not how the public perceives it that you have a huge chance of being very sick. I think people think it is more likely the baby will have some major malformity or illness, but it is still more likely the baby will be fine.

mattbrowne's avatar

Complementing immune systems are favorable. And we notice this subconsciously when savoring the smell of our potential partners.

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