A research published in Nature Genetics reveals the molecular mechanisms that prevents mitochondrial DNA from being inherited from the father. The team, with the participation of Ramón Trullás, Anna Calderon, Margalida Puigròs and Petar Podlesniy from the IIBB-CSIC, discovers that mature spermatozoa do not have mitochondrial DNA because they block access to the mitochondria of the transcription factor essential for mitochondrial DNA to replicate. The research shows that mature sperm do not have mitochondrial DNA because transcription factor A, unable to access the mitochondria, re-localizes to the nucleus.