If 2 brothers were suspected of being a child's father, could DNA testing determine which brother?

[raccoon]

(I don't need to know this for RL; it's happening in a soap opera.)

[GreenPartyVoter]

1. I should think so. Unless they are carbon copies of each other, right?

[lisa58]

2. lol

[babylonsister]

3. It worked on 'Brothers and Sisters'. I say yes! nt

[eShirl]

4. if they were identical twins, definitely not

for non-identical brothers, I would think it would be possible

[pokerfan]

18. Even if they were identical twins

http://www.livescience.com/health/080221-twins-not.html">Identical twins may not be nearly as identical as once believed

[LostinVA]

5. Definitely, unless they were identical twins

[mike_c]

6. and what if the mother was their SISTER?

I mean, let's not miss any of the dramatic possibilities here! :rofl:

Note to self: use this question as a genetics practice problem in BIOL 105.

[Thor_MN]

15. Then concentrate on the Y chromosome, which the sister could not share with her brothers.

[mike_c]

17. but that makes the brothers indistinguishable...

...since they both have copies of the same Y chromosome-- the only one available to any of the siblings if they have a common father. No, you'd have to use non-sex-linked alleles and find loci that are not shared by the two brothers, who, as others have pointed out, are hopefully not identical twins.

If they're identical twins? I dunno-- maybe look for different patterns of post-divergence X inactivation? I don't know.

I need to remember to ask one of my geneticist colleagues!

[HiFructosePronSyrup]

7. If they were identical twins it would be very difficult.

And perhaps prohibitively expensive.

[aquart]

8. Y&R?

They weren't able to rule Cane out. They said it was possible that he was the baby's father. But that was when they had no sample from the other brother to compare.


Actually, the dates rule Cane out. Chloe's pregnancy was more advanced than she told anyone and the hospital spotted that right away. I believe the correct dates are still in her record.

[Ilsa]

10. Yep. Average size baby with vernix = full term, not preemie.

And Cane and Billy are only half-brothers. So John Abbott's gift of DNA must be showing up in the next generation.

[raccoon]

11. Yes, it was Y&R. nt

[bluestateguy]

9. In Thomas Jefferson's family

Jefferson's relatives insist that the DNA tests show his brother to be the father of Sally Hemmings' children.

If that's what they want to believe, then I guess that's their right.

[Warpy]

12. Only if they were identical twins would there be a problem

because ordinary siblings are genetically quite different.

[Hoopla Phil]

13. Yes but it will be expensive.

There are different kinds of tests. The more accurate the test the more expensive. This would require a very accurate test.

[sinkingfeeling]

14. Not if they're identical. Yes, if they're fraternal, just like any other siblings.

[HamdenRice]

16. Maybe they are getting at the Y-chromosome problem? You could not use it

The Y chromosome is often used to trace paternity in the male line because each male child has exactly the same Y chromosome as his father -- unlike every other chromosome which trades some genes with the mother.

So, for example, the Hemmings family could prove that they were descendants of the Jeffersons by focusing only the the Y-chromosome. But they could not rule out that the Hemmings were descendants of Jefferson's brother or certain other male relatives. (But other historical evidence pretty much showed conclusively that having limited their descent to the Jefferson male line, it was Thomas Jefferson).

So you could not use the Y chromosome to tell whether a male child is the son of one or another brother.

You could use other chromosomes, however.

[muriel_volestrangler]

19. A UK soap was there a couple of years ago, and the Daily Telegraph got the answer 'yes'

from a genetics prof:

Then there is the question of whether the DNA test will be able to establish paternity given that they are brothers. Yes, say some, no say others, all advancing their own genetic theories.

For the definitive answer The Daily Telegraph turned to Prof John Burns, a clinical geneticist at the University of Newcastle. "There's no difficulty in testing between brothers," he assured us. "Basically brothers will share half of their genes in common and so the markers that we use for paternity testing are sufficient to discriminate. Unless we are dealing with identical twins.

"But Will and Ed are not identical twins".

Could any other factors affect the paternity test? Well, yes, it seems. The scriptwriters could have a field day and introduce some serious genetics into their everyday story of country folk. George could turn out to be a genetic freak. Mosaicism and chimaerism are two conditions which produce genetic changes which technically could make it impossible to assertain paternity.
...
"That is genetics that I don't even bother to explain to the first- year medical students and I think it would be too complicated for listeners of The Archers, actually".

http://www.telegraph.co.uk/news/uknews/1501634/An-everyday-story-of-infidelity.html

[marksmithfield]

20. are you sure you aren't in a bit of a bind?