Male and female genomes
We inherit a complete genome from our mother and another from our father
Every person’s genome is different, so the one we inherit from our father is not the same as the one we inherit from our mother – and it even appears that genomes may be engaged in a genetic ‘tug of war’ within a developing embryo.
It has been discovered that chemical modifications to DNA can be stably passed on when a cell divides. This ‘imprinting’ process controls whether a gene is active or not.
An example of parental imprinting is the insulin-like growth factor system, which has a strong influence on the size of a baby. The logic is that the genome inherited from the father works to maximise the growth of the offspring, to give it the best chance of survival when it is born. The maternally inherited genome, though, limits the size of the offspring and protects the mother, so she can go through further pregnancies.
So parents’ genomes may be constantly battling with one another, driven by evolutionary pressures to ensure that their DNA survives and spreads.
However, in each newly fertilised egg there is another form of DNA – mitochondrial DNA. Mitochondrial DNA is inherited directly from the mother, without any mixing or shuffling, and is housed in energy-producing powerhouses in the cell called mitochondria. This means that in each of our cells we keep a record of our grandmother’s genome, and her grandmother’s genome, and so on and so on, all the way back through time along the maternal line.Lead image:
Adam Nieman/Flickr CC BY
- A lesson plan on mitochondrial DNA from the BBC
- Epigenetics and inheritance
- Beckwith–Wiedemann syndrome demonstrates a role for epigenetic control of normal development (2003)