Inbreeding question?

Question

If we had a perfect set of DNA, RNA, whatever. Would imbreeding be a non-issue? Is inbreeding bad because the child has a greater chance of receiving a "bad" set of DNA? Not that I want to have sex with my sister or anything (eeeaaaacccc yuch!) don't get that impression please. I am just curious, because of the whole Adam and Eve thing. Because if their children had children as the Bible says it does they must have inbreed. If we all have a common male ancestor does that mean we are all inbreed. This is more of a funny question than a serious one, so dont get all pissy with me.

Also, my fathers side is from Germany and my mothers side is of mixed European decent. When my (ex)girlfriend and I were taking a genetics course we analyzed our mitochondrial DNA and found we had a common ancestor (must have been a female ancestor because mitochondrial DNA mutations are carried by the female?) But she was Vietnamese, if we had kids that wouldn't be inbreeding right? That would make no sense.

Answer 1

The average human being has between 5 and 7 serious genetic defects (Poisson distribution). Since these are usually recessive, there is a relatively small chance that it will be expressed in the next generation given random partner selection. Hemophilia is just such a defect that afflicted the royal houses of Europe.

For each defective gene between a set of parents F0, there is a 1/4 chance that a pair of siblings F1 will both get the defective gene, and a further 1/4 chance that the offspring of such a pairing F2 would get 2 copies of the defective gene. So, for each defective gene in the F0 generation, there is a 1/16 chance of a genetic defect being expressed in the F2 incestuous offspring.

With 10 genetic defects in the F0 generation, the chance that an F2 offspring is unaffected or normal is:
(15/16)^10= .524

With 14 genetic defects in the F0 generation, the chance that an F2 offspring is unaffected or normal is:
(15/16)^14= .405

So that an incestuous pairing results in normal children less than half the time! That is just for parents in F0 that are unrelated. If they are related, things are much worse. Ancient people would have interpreted this as a punishment from God.

Regarding your mitochondrial DNA and your lab partner/ex-girlfriend, you only got mitochondria, with their DNA, from your mother, and so did she. You would not contribute mitochondria to your offspring.

Using principles of population genetics and Markov chains, it is not to difficult to see that, by repeatedly ascending the maternal ancestral line, we must eventually merge all such lines and find a single matriarchal ancestor. Mitochondrial geneticists have dubbed this matriarchal ancestor "Eve."

No, it wouldn't be inbreeding to have children with her. It would just be "wrong" to breed with an EX-girlfriend.

Answer 2

Ok first of all inbreeding to humans is technically only "morally"wrong......ok I will add there is a higher risk of some rare genetic diseases being seen more in inbreeding populations, but otherwise the children are not deformed or anything else ( there is probably a LOT of people walking around who have no idea they are the result of inbreeding....they would almost certainly be perfectly normal).
For example the Armish in Pennslyvania are a population ( starting from a small german population) who do not "breed" with the general population....there is a higher incidence of polydactly ( 6 digits on hands/feet) because of the relative inbreeding in this population.

I assume that you have done the mitochondrial DNA test that the guy who wrote "Seven daughters of Eve"...forgot his name......I thought that these were for european "female ancestors"...but basically yes there is a lot more inbreeding than you would think (look at the Royal families of europe....heck the Queen (of England) is married to her first cousin!)...BUT the time factor has a lot....from what I remember in the book its been THOUSANDS of years since there was a "common ancestor" so I would not consider it inbreeding....unless it was with a CLOSE relative ( ie immediate family).

Answer 3

The general concern with inbreeding is the emergence of "bad" recessive genes. If two individuals with similar genetic make-up, like two members of an immediate family, mate the chance of recessive traits popping up increases. This is because there is a greater chance of the two individuals having the recessive gene or genes and then the genes pairing in the offspring.
There used to be genetic diseases that cropped up in royalty because they would only marry and have children with other royalty. Many times the royalty would be related in some fashion or another and the genetic pool progressively became more shallow.
As for your ex-girlfriend and you, in my opinion you two are far enough removed from each other in ancestry that I don't think that it would have been a problem. However, I am by no means an expert.
Here is something to chew on. I heard that a group of individuals went into Asia to do genetic sampling and looked at mutations in the Y chromosome to trace ancestry. They found that around 16 million individuals are descended from one man that lived around 1000 years ago. It has been theorized (not confirmed) that man was Genghis Khan.

Answer 4

In fact it's very difficult for people to avoid "breeding" with others that are "totally" unrelated, because it doesn't take very many generations before a sizeable percentage of the population to carry the genes of a particular ancestor, thus making very likely that any two people could have the same ancestor. On the flip side, even babies conceived by first cousins aren't significantly more likely to come down with a genetic disorder than two people picked at random, in spite of the hillbilly stories we hear. If it were true that babies of closely related couples were very likely to be malformed, then animals in the wild which frequently encounter population bottlenecks wouldn't have survived so readily.

The danger of inbreeding actually lies in having a small genetic pool in a population for too long of a time, such as isolated villages existing for generations without outside contact. Even if everyone in the village had scrupulously avoided "inbreeding", genetic disorders are still far more likely to crop up than with random first cousin couples. A classic case in point are the royal families in Europe, who for centuries had to abide very strict rules against close relation marriages. In spite of such widely observed rules, they nonetheless suffered from a higher incidence of genetic disorders than the general population who paid no attention to such things. The problem was that the genetic pool among the European royality was just too small for too long.

Answer 5

If by "perfect set of DNA, RNA," you mean no
'harmful` genes in the pool, then the only
negative result would be a population so
uniform, the it would be extremely vulnerable
to infection by a well fitted antagonist.
I don't think we've found all the 'bad` genes
yet, so this is not easily guaranteed.
As to the "common female ancestor",
it might have been "Eve",
(the theoretical first african female human).

Answer 6

a) If you have no deleterious alleles, then it's okay, genetically, for you to marry your sister. If your sister also has no deleterious alleles, then your children may marry each other up until the time that one of them gets a deleterious mutation in the germ cell line.

b) Don't worry about mitochondrial DNA. You and your girlfriend are fine.

Answer 7

It really depends on who you ask, as there is no definitive answer.

The best research I have found on the subject was regarding theoretical space travel missions, and populating other planets.

They proposed that you would ideally need 160 people to ensure that inbreeding was not a serious problem.