Understanding how genetic variation is passed on from parent to offspring in a species isfundamental to understanding its evolution. Yet, little is known about the exact processescontrolling inheritance in fungi, for instance when the germ cell fate is defined, i.e., when thedistinction between somatic cells and the zygote forming cells happens. The assumption has longbeen that fungi have late rather than early on in development germline sequestration.Consequently, somatic mutations are assumed to be passed on to the offspring in fungi. However,there is a lack of molecular data confirming this assumption. In this project, I have traced thedistribution and frequencies of novel mutations within fruiting bodies of a fairy ring of aMarasmius oreades individual, with the ultimate goal to explore potential mechanisms forcontrolling inheritance of genetic variation in fungi. I called for putative mutations in high readdepth coverage Illumina sequencing data (aiming for 400X) from 36 different tissue samples,collected from seven different fruiting bodies, and was able to identify 40 novel mutations in thewhole dataset. Thirty-two of these 40 mutations were shared between several fruiting bodies,while the remaining eight were unique to a single fruiting body. In general, the number, as wellas the frequency, of mutations decreased from the stipe to the lamella and spores. However, fourof the identified mutations reached a frequency close to 0.5 in the spore samples they were found.These findings do not exclude the possibility of an early-sequestered germline in M. oreades, butalso could be indicative of intraorganismal selection. Although more studies are needed to drawany definite conclusions, the data presented here exemplifies the complexity of fungal geneticsand underscores the need of re-evaluation of old assumptions.