Not all our DNA is kept in the cell nucleus. More than three dozen of our 25,000 genes are actually stored in an organelle we inherit from mother. The mitochondrion is a sub-cellular energy-generating structure present in most body cells. Every copy in our body came from those within the egg. Dad’s mitochondrial DNA is ditched during sperm production. Researchers have identified a protein in fruit fly called EndoG, which helps with this elimination. Yet in mutant flies without EndoG the DNA is still expunged. So there must be some kind of back up. Mitochondria (shown in red) stretch along the length of developing sperm tails. Debris from these cellular ‘power stations’ is tidied (by proteins here coloured purple) into ‘waste bags’ (red blobs). In the flies without EndoG the male mitochondrial DNA gets scooped up too. This must be the fail-safe that ensures mitochondrial DNA remains female.
Written by Rebecca Hill
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