The world has seen many relationships end after the utterance of this sentence on the famous TV show, "Maury". As I was scrolling through Facebook the other day, I looked over at the "Now Trending" tab on the side and saw a link that said "
DNA: Father Failed Paternity Test Due to ‘Chimeric’ Genes, Researchers Say", so I of course clicked on it. What followed was very interesting. A couple from Washington used a fertility clinic to help them have a child. The pregnancy and birth went well, but they later found out that the child's blood-type did not match either parent, so they decided to do a paternity test, which the father failed. This lead them to assume that the clinic might have swapped the sperm samples with an unknown donor.
Simply put, a paternity test is done by taking saliva or blood samples from the child, mother, and father(s) in question and comparing the alleles to each other. The child's alleles should have several matches to the mother's and father's, some matches to a non-parent family member, and fewer to none matches to a stranger/non-family member (if the child has no matches, they are probably adopted).
The failed paternity test then led them to do a full DNA test on the father's and child's DNA, after which they found that there was a 10% match, suggesting that he was actually the child's uncle, rather than father. These tests were done using DNA from blood and saliva samples, so doctors then tested his sperm, which contained the match to the child. This phenomenon is called chimerism, which is when a person has extra genes/DNA that were absorbed from an unborn/miscarried twin in the womb. This theory of the man being a chimera supports the uncle results since the DNA in his gametes is ultimately from his unborn brother. Weird, huh?
What if the unborn twin had been a girl? Would that mean that this man's gametes would be eggs, and therefore make him unfertile, or would his sperm contain female DNA that would guarantee that the only children he and his wife could have were girls? The
news article I read only mentioned another case where the unborn twin was the same sex as the chimera, so it would be interesting to look into this possible scenario.