How does a spindle nuclear transfer work? How does the baby have the DNA of 3 people?
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It kind of doesn’t. At least, not normal DNA.
You probably already know that the mitochondria is the powerhouse of the cell. What you may not know is that mitochondria have their own, separate DNA. Most people most of the time get their mitochondrial DNA from their mothers: the mitochondria in sperm get destroyed (usually) before they enter the egg cell, and it’s the mitochondria in the egg cell that divide and power all the cells in your body. That mitochondrial DNA can be damaged or faulty for various reasons, causing congenital defects that are often incompatible with life. And if the mother carries the mutation in her mitochondrial DNA, there’s practically zero chance that it won’t be inherited by the fetus.
Spindle nuclear transfer is a procedure where they take a donor egg cell from another woman and carefully remove just the nucleus. That removes all of the cell’s normal DNA, but leaves the mitochondria and its DNA intact. Then, they take a fertilized egg from the prospective mother and carefully remove its nucleus and insert that nucleus into the donor egg cell. This way, the baby gets its mitochondrial DNA from the donor mother and does *not* inherit the damaged or faulty mitochondria from the biological mother.
Thus, the baby has three genetic parents: its normal cellular DNA comes from the mother and father, while its mitochondrial DNA comes from a donor mother. But *only* the mitochondrial DNA is not from its parents.
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