The the brain has cells packed with mitochondria; so

The article “Do you share more genes with your mother or your father?” by Dr. Madeleine Beekman from TheConversation explains why mammalian offspring carry more of their mother’s genes than their father’s genes. This isbecause the mitochondria that live in cells can only be gained from a mother. Mitochondria are the energy-creating factories of cells and are necessary to making cellular energy from food. Mitochondria used to be autonomous organisms, and have retained their own genome called mitochondrial DNA, or mtDNA. Tissue that needs lots of energy, such as the brain has cells packed with mitochondria; so mammals are more related to their mother thanfather. In plants and fungi, mitochondria do not have to come from the mother. Why does one kind of inheritance exclude oneparent completely? The reason is ‘uniparental inheritance’. The “conflict theory” is the idea is that mtDNA replicates freely in the cell so that the number of copies increases over time. The more copies there are, the more likely some will be carried by daughter cell when that cell divides. If all mtDNA comes from one parent only,thenmitochondrial DNA within a cell are clones. They are competing with exact copies of themselves. If organelles werederived from both parents, four grandparents, and so on, this would be bad news because different clonal lineages of mtDNA would be competing with each other and the faster mtDNA replicates, the more copies it produces and the more likely it will spread to the next generation of cells. Ultimately, the slower reproducing organelles will be eliminated from the cell genealogy because,  the smaller an organelle’s genome, the faster replicates. At some stage, genomes will be so small that the organelles will cease to function properly and the cell will suffer. Recently a simpler explanation was offered: what if the mixing of mitochondrial lineages within the same cell is costly in itself?This assumption explains the strange inheritance of mitochondria in a model.  Mice that were experimentally constructed so that they carried mitochondria from both parents were less active, more stressed and cognitively impaired. It seems that carrying mitochondria from both parents is bad for offspring and that all the components of animal reproduction were specifically designed for efficiency and preservation. 

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