A study published in Nature Communications today, suggests that the relationship between an individual's genes, environment, and traits can significantly change when a single, new mutation is introduced.
"Individuals have genetic and environmental differences that cause these mutations to show different effects, and those make it difficult to predict how mutations will behave," explains Ian Ehrenreich, a lead author of the study and biologist at the USC Dornsife College of Letters, Arts and Sciences. "For example, mutations that break the cell's ability to perform DNA mismatch repair are linked to colorectal cancer, but some individuals that harbor these mutations never develop the disease."
A growing number of large-scale, genome-wide association studies have revealed which genes are linked to certain diseases, behaviors, or other traits. These studies overlook how interactions between genetic differences, the environment, and new mutations—or background effects—differ from individual to individual.
"Mutations that behave unpredictably are most likely quite rare. However, that makes them difficult to detect and measure in those studies," Ehrenreich adds.
Ehrenreich and his team examined the impact of mutations through a study on yeast. They introduced particular gene deletions into a large number of progeny from a cross of two strains of yeast. Then, they systematically mapped the interactions between the pre-existing genetic differences and the mutations. By conducting their work across several environments, they were able to characterize how these interactions between mutations and genetic differences change across conditions.
The authors found that background effects result from many, often environment-specific, interactions between mutations and genetic differences. In fact, most of these interactions involved multiple genetic differences interacting with not only a mutation, but also with each other and the environment.
These findings imply that background effects result from complicated interactions between mutations, pre-existing genetic differences, and the environment.