This might be a little to complicated for the grade 6′s but you might find it interesting.
There is the story of Mrs. Lydia Fairchild, who’s along with her children and ex-husband were required to take a DNA test for legal reasons. The results of the DNA test are almost unbelievable. The ex-husband and the children were confirmed matches but Lydia’s DNA did not match her children!
How can the mothers DNA not match her children’s?
This led at an impossible situation where Lydia was accused of things like stealing, and implanting another woman’s embryos.
The answer is that Lydia is a Chimera. Different parts of her body have different DNA profiles.
In rare cases, 2 eggs are released and can be fertilized leading to the birth of twins. In extremely rare cases, shortly after conception the developing embryos may ‘bump’ into each other. The next 96hrs (4 days) are then very important. One of three things can happen. The embryos separate, the embryos co-develop, resulting in siamiese twins, or the embryos merge, resulting in a chimera.
When 2 embryos merge each embryo takes over the development of different body parts. The blood could be developed by one embryo and the skin by the other. There is no set pattern for which DNA sequence develops what part of the body, it seems almost random.
Back to the story of Mrs. Farichild. Further testing from DNA samples taken from different parts of her body, not just a blood sample, proved that she was in fact a chimera, and that while the DNA profile from her blood did not match her children other body parts did match. She was in fact the mother of her children.
In a strange way Lydia Fairchild and other chimeras are their own twin.
