Intragenomic conflict

Intragenomic conflict refers to the evolutionary phenomenon where genes have phenotypic effects that promote their own transmission in detriment of the transmission of other genes that reside in the same genome. The selfish gene theory postulates that natural selection will increase the frequency of those genes whose phenotypic effects cause their transmission to new organisms, and most genes achieve this by cooperating with other genes in the same genome to build an organism capable of reproducing and/or helping kin to reproduce. The assumption of the prevalence of intragenomic cooperation underlies the organism-centered concept of inclusive fitness. However, conflict among genes in the same genome may arise both in events related to reproduction (a selfish gene may "cheat" and increase its own presence in gametes or offspring above the expected according to fair Mendelian segregation and fair gametogenesis) and altruism (genes in the same genome may disagree on how to value other organisms in the context of helping kin because coefficients of relatedness diverge between genes in the same genome). Autosomic genes usually have the same mode of transmission in sexually reproducing species due to the fairness of Mendelian segregation, but conflicts among alleles of autosomic genes may arise when an allele cheats during gametogenesis (segregation distortion) or eliminates embryos that don't contain it (lethal maternal effects). An allele may also directly convert its rival allele into a copy of itself (homing endonucleases). Finally, mobile genetic elements completely bypass Mendelian segregation, being able to insert new copies of themselves into new positions in the genome (transposons). In principle, the two parental alleles have equal probabilities of being present in the mature gamete. However, there are several mechanisms that lead to an unequal transmission of parental alleles from parents to offspring. One example is a gene drive complex, called a segregation distorter, that "cheats" during meiosis or gametogenesis and thus is present in more than half of the functional gametes.