The genes in mitochondria, which are the powerhouses in human cells, can cause fatal inherited disease. But replacing the bad genes may cause other health problems.
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In 2010, scientists plopped the genetic material of one Mycoplasma bacterium into another type to create the self-replicating cells shown above. Six years later, they've come out with an even simpler synthetic organism that has fewer genes.
Thomas Deerinck, NCMIR/Science Source
An image of researchers at Oregon Health & Science University removing the nucleus from the mother's cell before it's inserted into the donor's egg cell.
Courtesty of Oregon Health & Science University