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From the struggle of selfish genes, to the path of evolution

The progress in genetic research, with all its enormous importance, may also bear fruit in the "less practical", but very fascinating, field of understanding the process of evolution, which is a first-rate scientific challenge, and of unrivaled cultural importance, as well as shedding light on the mysteries of life.

By David Issachari

Scientists from Australia are now reporting on findings obtained from small marsupials (Platypus (a flat-footed duck) and Opusium (a species of tiny marsupial), found in Australia), both for the study of the battle of the species and for understanding the processes that cause cancer.

By comparing certain genes in these two animals, the researchers from the Duke University Medical Center found evidence for the origin of a mechanism called "genomic imprinting." A classic Mendelian mechanism, in which there is a mixture of genes (alleles) where one is dominant and the other is recessive. This mechanism may help in the question of the evolution of mammals as well as in questions related to the development of carcinogens.
The existing theory regarding the evolution of genomic imprinting is based on the idea of ​​a "battle of the sexes". A battle in which paternal imprinted genes "struggle" with maternal imprinted genes. The former push the fetus to overgrow, and the latter do not and this is due to considerations of saving the mother's energy (the theory of the "selfish gene" at its best D.I.). According to this theory, animals that do not excel at long pregnancies, such as marsupials, whose pregnancy takes place outside the womb, and monotremes (Australian mammals that lay eggs, the most primitive form of mammals), are not supposed to be "genetically imprinted".
Student Wright Killian and his supervisor Randy Girtel, his supervisor report that a certain gene called M6P/IGF2R is imprinted in opusium but not in platypus. This indicates that the separation between these two creatures occurred further in the past than previously thought. These genes code for the creation of "insulin-like growth factor". 2 "IGF2R" These genes are maternally imprinted, M6P/IGF2R, 2IGF is paternally imprinted.

The researchers found that the different expression of the genes is the result of a "struggle between species", which takes place during the embryonic stage, when the fetus strives to leave the womb and the pouch, and hurries to reach its mother's nipples. A delay at this stage for him is fatal in the run between dozens of offspring to a mother with about thirteen nipples. On the other hand, in the duck born from an egg, there is no such problem, and therefore there is no competition between its genes.

This feature of genetic imprinting has also remained in advanced mammals and even in humans, although it has no role in these mammals. Their essentiality for the development of developed mammals is not yet clear. As a result of their dysfunction, they are a target for developmental diseases and cancer. Indeed, it will be found, for example, that in 60% of liver cancer cases these genes, M6P/IGF2R, are found as imprinted.

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