Long-run evolution of B chromosomes is mainly made up by an evolutionary arms race between these selfish genetic elements and the standard genome. The suppression of B drive is one of the clearest expressions of genome defense against B chromosomes. After drive neutralization, the B is condemned to extinction unless a new variant showing drive can emerge and replace it. This paper reports the first empirical evidence for the substitution of a neutralized B variant by a new selfish B variant. Such a polymorphism regeneration has recently taken place in a natural population of the grasshopper Eyprepocnemis plorans.

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We present an HIV-1-infected patient with a profile of transmitted drug resistance (RT M41L, E44D, V118I, L210W, T215D) sustained during more than 10 years in the absence of treatment. Clonal analysis of different plasma and cellular samples within this period did not reveal any reversion to the wild-type genotype.

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