Yeast single environment evolution

Many organisms live in predictable environments with periodic variation in growth conditions. This is especially true for parasites that live inside host systems, as well as for cells in multicellular organisms. Living in a near-constant condition can lead to loss of gene functions that are not essential for survival in that environment. On the other hand, it can enable populations to explore the genotype space, and allow them to accumulate cryptic genetic variations. These variations can help populations survive through occasional occurrences of stressful conditions. However, which of these two types of mutations shape population fitness remains largely unknown. In the current work, we address this question by laboratory evolution experiment of replicate yeast populations in a nutrient-rich environment (YPD medium) for 1000 generations. We sequenced the genomes of the evolved lines (N lines) and the ancestral lines (A lines) to identify mutations that arose during these 1000 generations. The experiment was performed in triplicates.