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Man Fails Paternity Test Because Unborn
Twin Is the Biological Father of His Son
October 26, 2015 | by Justine Alford
Prepare to have your mind blown. This is the
fascinating case study of a man who failed a
paternity test because part of his genome
actually belongs to his unborn twin. This
means that the genetic father of the child is
actually the man in question’s brother, who
never made it past a few cells in the womb.
Yes, this sounds completely crazy and like a
headline you might read in a supermarket
magazine. But before you write it off as that,
let’s go into some more details.
It all starts off with a couple in the U.S. who were having trouble conceiving their second child.
They decided to seek help and went to a fertility clinic, where eventually intrauterine
insemination was performed. This involves washing and concentrating sperm before inserting it
directly into the uterus of a woman around the time of ovulation to boost the chances of
fertilization.
The assisted conception worked, and nine months later the happy couple welcomed a baby boy
into the world. But then things started to take a turn for the weird. Testing revealed that the
child’s blood type didn’t match up with his parents’.
“Both parents are A, but the child is AB,” Barry Starr from the Department of Genetics at
Stanford University told IFL Science. “There are rare cases where that can happen, but their first
thought was that the clinic had mixed up sperm samples.”
The couple therefore decided to take a standard paternity test, which to their dismay revealed that
the man was not the child’s father. So they took another test, but the results were the same. At
this point, mixing up samples didn’t seem too far-fetched, but the clinic had only dealt with one
other intrauterine insemination at the same time as this couple, which involved an AfricanAmerican man, and given the child’s appearance this didn’t match up.
This was when Starr was contacted by the couple’s lawyer, who suggested that they take a more
powerful test: the over-the-counter 23andMe genetic service. This was because this particular
test is good at looking at family relationships. The results that came back were pretty surprising,
suggesting that the child’s father was actually his uncle, the man’s brother.
At this point, Starr’s team decided to delve a little deeper, with the idea that the man could
possibly be a “human chimera,” i.e. an individual with different genomes. It’s actually not
uncommon for multiple fertilizations to happen in the womb even when only one child is born.
What can sometimes happen is two independent early embryos, at this stage just clumps of cells,
actually fuse together and go on to develop normally as a single individual.
To test this theory, DNA samples were taken from both the cheek of the father, which was used
for the original paternity tests, and also his sperm. Once again, the cheek cells didn’t match up
with the child, but the sperm sample told a different story.
Supporting the human chimera idea, what they found was a “major” genome, accounting for
roughly 90% of the sperm cells, and a “minor” genome that only represented about 10%, Starr
explained. The major genome matched up with the cheek cells, but the minor genome was
consistent with the child’s DNA.
“So the father is the fusion of two people, both the child’s father and uncle. That’s wicked cool,”
said Starr.
Answer the following Questions based off the above passage:
1. Define genome:
2. What is a fertilized egg called?
3. What is the purpose of a paternity test?
4. How did scientist first discover that the child did not have the same genetic makeup as his parents?
5. What is human chimera?
6. What form of reproduction created a genetically different offspring?
7. How does this article relate to topic 5?
8. Summarize this article in a few brief complete sentences.
Answer the Following sexual reproduction Regents questions related to this topic……Circle your
answer
9.
10. One function of the male reproductive system in mammals is to
1.
2.
3.
4.
11.
produce insulin necessary for sexual reproduction
transport eggs necessary for fertilization
allow for delivery of gametes needed for reproduction
provide protection for the developing zygote
12. All the information necessary for growth, development, and eventual reproduction of
sexually reproducing organisms is present in
1.
2.
3.
4.
sperm cells, only
egg cells, only
zygotes
either sperm cells or egg cells
13. Answer graph question below:
14. Which processes lead to the greatest variety of genetic combinations?
1.
2.
3.
4.
asexual reproduction and cloning
meiosis and fertilization
meiosis and mitosis
cloning and mitosis