Could my sister and I give birth to our father?

For what it's worth I have no sister.

Ok, so both my theoretical sister and I have half of the genes from our mother and our father, just different combinations of those two's genes.

Is it possible, that a sperm I deliver to my sister's egg would have precisely half of the genes of father, the egg the other half meaning, in essence, we'd produce a "clone" of my father?

Granted, the odds I suspect would be astonomical, but is it "possible?"

 

I can't past the part where this would require you to impregnate your sister.

 

It's to do with chromosomes. You all have 23 pairs.

Firstly, you and your sister between you would have to have the complete set of 46 chromosome halves that make up your father.

Whatever set your sister got doesn't matter, but you would have to have been given the exact opposite set, which has a probability of 1 in 2^23 = (1 in 8,388,608)

Then to bring these back together in your child, you'd have to donate those 23 halves and none of the halves you got from your mother. And your sister would have to do the same. So that is 1 in 2^23 for each of you.

So the total probability is 1 in 2^23 * 2^23 * 2^23.

= 1 in 590,295,810,000,000,000,000.


But the odds are a bit better than that, because you have chosen your sister (rather than just any sibling), which halves the odds.

Then there is mitochondrial dna, which comes entirely from the mother who donated the egg, which in turn came from her mother, so this component is not possible.

 

Jadzia just did all the math for us, so yay!

There was a book I wrote where a guy got thrown 110 years into the past, and looked up his great-grandmother so he'd at least have someone with a familial connection to talk to. I almost went down the road of having him be his own great-grandfather, but the situation was squicky enough as it was.

 

So about 1 in 300 quintillion!

 

That sounds vaguely like an episode of "Futurama". A classic one too. All I know about siblings procreating is I've always been told it almost inevitably leads to mentally ill offspring. I don't know if there's any truth to that, it's just something I was told a long time ago.

 

Yes, the Futurama episode was kind of the inspiration, although there are plenty of other "I'm my own father/grandfather/whatever" stories out there, too!

I don't have any studies handy, but close relatives breeding with each other leads to birth defects. For proof, all you have to do is look at how dog breeding is done. Ever notice how certain breeds have a laundry list of medical problems and defects? That's because breeds are created and maintained through inbreeding. A shallow gene pool increases the likelihood of harmful recessive traits being expressed.

It was a big problem in the royal families of Europe, too. If you were short on available wives of the proper stature, well, go for a sister or cousin. Ick.

 

Yeah, she beat me to it

 

^ Then you'll notice my deliberate mistake

 

Oh, absolutely.

But i'm sure you can explain it much better than I.

 

Inbreeding itself does not cause mentally ill or deficent offspring. Your genes don't know your brother's or sister's or cousin's genes from Adam. What does happen is that there's a greater chance that a recessive trait you're carrying will meet-up with a recessive trait your relative is carrying and will activate a recessive genetic trait that'd cause a "defect" in the child. This could be any number of genetic problems from various diseases like Huntingtons, diabeties or things along those lines or simply blue eyes.

But inbreeding, the act itself, doesn't cause a deformed or mentally-deficient child. It simply makes the gene pool shallower and makes certain genetic problems, already in your famly, more likely.

 

The odds are actually considerably smaller than that. During meiosis (the process that segregates genetic material during gamete production) there is considerable crossover and homologous recombination going on. That means that those chromosomes do not remain intact as they are, but they recombine with the other set of chromosomes and essentially mix the genetic material between the two sets. The numbers you came up with assume no recombination. Once that is figured in the odds grow much much smaller.

 

Have you been drinking from the Gulf of Mexico?

 

... Why?

 

"I always say, when you turn the family tree into the family bush, you just can't hide as much beneath it!"
-Minister Virini on Centauri noble bloodlines, Babylon 5

 

“If your family tree does not fork, you might be a redneck!”
— Jeff Foxworthy

 

You're wondering?