Mutation accumulation lines are used to determine the amount of variation added each generation due to mutations in C.reinhardtii.

Survival hinges on the malleability of DNA in response to environmental demands; mutations arise from accidental alterations of DNA sequences and provide the raw material for evolution by introducing genetic variation. Gene expression can be used to link the effect of mutations on the genome – genotype, and its respective phenotypic change. It has been used to study de novo mutations and their effects on gene networks, regulation, and other phenotypic traits including fitness. Here, we sequenced the mRNA of 28 mutation accumulation lines derived from two independent wild-type genotypes of the green algae Chlamydomonas reinhardtii. We found the median mutational variance was up to 18 orders of magnitude higher than past studies possibly indicative of a more responsive transcriptome in microbes. We calculated the amount of expression variation contributed per mutation over several generations and found that high expression genes underwent a lower total expression change than that of lower expression genes. Genes that underwent significant expression change did so in both directions' indicative of trans-acting effects. Surprisingly, we did not find a correlation between fitness and expression change, though future studies can disentangle the individual phenotypic and fitness-related effects of each mutation rather than the collective.