How can someone genetically look like the uncle of a child when they are actually the father?
It is all to do with the father having two sets of DNA, namely from being what is known as a human chimera. This can occur when fraternal twins fuse together very early in development. Because fraternal twins do NOT have identical DNA, the end result of this fusion is someone with two sets of DNA. Some of the father’s DNA must be from the first twin and the rest have the DNA from the second twin.
There is one particular recent case of this occurring when a couple (who will remain nameless) used a fertility clinic to conceive and were furious when the child’s blood type did not match with either of theirs. They originally assumed that the clinic had made a major mixup such as using the wrong sperm sample.
Luckily, a complex DNA relationship was then utilised to reveal that the father must have been a human chimera. If a DNA paternity test had been used this detail may have been missed, as this may have wrongly concluded only that he is not the father of the child. With a more complex relationship test, they were able to determine what kind of relationship he had with the child genetically and interpret what may have caused him to appear as if he was the uncle of the child rather than the father.
This was particularly evident with the DNA in the cells from the lining of the father’s mouth, using a mouth swab to collect a sample of saliva for testing, must have been from one twin and the DNA in the sperm that fertilized his wife’s egg was from the other twin.
Choosing The Right DNA Test
The choice of DNA test was important from more than one point of view, as the couple were reassured that they were the biological parents of the child and legal action against the fertility clinic had been averted. Had the wrong type of testing been used the clinic may have been wrongly attributed to making unforgivable errors and the couple would have possibly believed that the child was not biologically theirs.
If you too need a DNA test, but are confused when it comes to deciding what test it is the best for your circumstances, then give AlphaBiolabs a call on 0333 600 1300. Our support team will be able to guide you in the all the aspects of DNA testing including what tests are suitable, what the tests involve (how the sample is collected for example) and any guidance you might require throughout the process.
Misleading Blood Type from Blood Test
In this particular case the couple knew that it could not have been a complete mix up with both the father’s sperm and the mother’s egg as they used a method called intrauterine insemination, which basically means that the man’s sperm was placed directly into the wife’s womb by the clinic.
She became pregnant and all seemed fine with the baby, but a blood test showed that its blood type was AB while both parents were A. Although there are rare cases where A parents can have an AB child, they wanted to narrow this down for a full explanation, so they turned to a DNA test to get the answers they needed.
Given that the parents visited a fertility clinic the best explanation from the DNA test results was most certainly that the father is a chimera. The DNA in the fertilising sperm was able to contribute a B to the child’s blood type, giving the child type AB blood, even though the DNA from the mouth swab did not have a B.
More Information About Human Chimeras
Human chimerism does not only occur with twins, those who were not twins are thought to have blood cells from a twin that died in early gestation (period of time between conception and birth). Twin embryos often share a blood supply in the placenta, allowing blood stem cells to pass from one and settle in the bone marrow of the other.
In vitro fertilisation (IVF) is also contributing to the number of human chimeras. To improve success rates of this method, two or more embryos are placed in the uterus so women who have IVF have a higher likelihood of twin pregnancies than usual. The more twins that there are the higher the population of chimeras will rise.
In more common cases, people can also be microchimeras and carry smaller numbers of foreign blood cells that may have passed from the mother across the placenta, or persist from a blood transfusion.