This means that even though we inherit an equal amount of DNA from each parent, the paternal line is mostly found to govern how a person develops into an adult — especially in regards to their health. The findings could give scientists more insight into how diseases and conditions are caused by the expression of thousands of genes, of which several hundred imprinted genes — rather than out of the 95 initially thought — could be in favour of the father.
James Crowley, assistant professor of genetics, selected strains of mice that descended from a subspecies that evolved on different continents and each type was used as both father and mother. When the nine baby mice reached adulthood, the researchers measured gene expression in four different kinds of tissue, including RNA sequencing in the brain.
So imagine that a certain kind of mutation is bad. The reason behind the evolution of so-called uniparental inheritance has long been a mystery among evolutionary biologists. One thing was clear: it better be for a good reason. Mammalian males go through the bother of actually tagging the mitochondria in their sperm so that it is easier to destroy them after the egg has been fertilised.
In plants too, the mitochondria from one parent are actively destroyed, this time before fertilisation takes place. The idea is that mtDNA replicates independently within the cell, so the number of copies increases over time. And the more copies there are, the more likely some will be transmitted to the daughter cell when that cell divides. If all mtDNA comes from one parent only, then mtDNA within a cell are closely related to each other, as they are all clones.
Hence, there is not much scope for competition, as copies of the mitochondrial genomes are basically competing with exact copies of themselves. But imagine what could happen if organelles were derived from both parents, the four grandparents, and so on ad infinitum. This would set the scene for a genetically variable population of organelles in every cell. And this could be bad news as now different clonal lineages of mtDNA are competing with each other. 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 organelle lineage will be eliminated from the cell lineage. Thus, competition among organelles within cells selects for smaller genomes. At some stage genomes will be so small that the function of the organelle is affected. Basically, epigenetics influence the way your DNA is actually expressed.
It can also affect the way the genes you have are read — and the proteins they produce — across your lifetime. Take, for example, a study in Nature Genetics that showed the expression of thousands of different genes in mice varied depending on whether they came from a mom or a dad.
Researchers think differential expression can also change your mental and physical wellbeing. If mom has a predisposition toward a given disease, you may still inherit it. But if your dad passes on genes that pass on an illness or a mutation of some kind, you may be more likely to be sick yourself, simply because his genes are more likely to be expressed.
Still, researchers are making headway, and many think it may start with a war all the way back in the womb. In order to stop themselves from destroying the tiny fetal invader, their bodies have to impair their own healthy immune system responses.
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