01/06/2024
Did You Know?
A DNA test can show a negative result for a biological parent due to a condition called chimerism!Chimerism is a rare condition where an individual has two or more genetically distinct sets of cells in their body.
It occurs when two fertilized eggs (zygotes) or early embryos fuse together during the early stages of development. This results in a single individual who has two distinct sets of DNA, one from each zygote.Look at this Scenario Example. This will help you understand this phenomenon.
Consider a man named John who is a tetragametic chimera. This means that during his early development, two fertilized eggs (each with its own unique set of DNA) fused to form a single individual. As a result, John has two distinct sets of cells in his body, each with different genetic profiles. We will refer to these as DNA Set A and DNA Set B.
John's body produces s***m from both cell lines. This means some of his s***m carry DNA Set A, while others carry DNA Set B.
When John conceives a child, the s***m that fertilizes the egg could carry genetic material from either DNA Set A or DNA Set B.
The distribution of which genetic material (DNA Set A or DNA Set B) is passed on to each child is random, leading to genetic variability among his offspring.
Imagine John has two children, Alice and Bob, with his partner, Mary. Hereโs how the genetic inheritance might play out:
Alice: The s***m that fertilized Maryโs egg carried DNA Set A.
Bob: The s***m that fertilized another of Maryโs eggs carried DNA Set B.
If a DNA test is conducted using a sample from a part of John's body that has DNA Set A and compared with Aliceโs DNA, the test would show a match, confirming John as Alice's biological father.
If the same test is conducted using a sample with DNA Set A and compared with Bobโs DNA, the test might incorrectly indicate that John is not Bobโs biological father because Bob inherited DNA Set B.
Note: Different tissues might carry different genetic profiles in chimeric individual.