Except in a few outliers such as some lizards, we animals get half our genes from our mother and half our genes from our father. It goes deeper than that.
For many genes that have the same function in both mother and father, one copy gets naturally tagged and turned off - for one gene it may be the father’s copy, for another it may be the mother’s. It’s a 100% normal event in our development. Selective use of genes is even more pronounced in females. They get two X chromosomes, one each from mother and father. In each cell of a female’s body one or the other of those is just turned off.
Decades ago, researchers reorganized mouse embryos at the stage where they have two (pro)nuclei, one from the mother, one from the father. If one were removed, sometimes the embryo developed. Digging deeper, five researchers in two groups created embryos with the normal two pronuclei but in some both pronuclei came from a female and in others both came from a male. The embryos did not survive or did not develop.
Further research led to the discovery of genetic imprinting or marking, including differences between mother and father. There’s a lot more to the story, then, of just the DNA sequences. Three different kinds of markers on the DNA at various places make a whole new ball game. We’re still learning how it’s played.
This has been an outreach activity of the Las Cruces Academy, viewable at GreatSchools.org
Source: Nature, 23 May 2024, pp. 763-5.