A closer look at the reproductive behavior of yeast reveals how genetic parasites spread

In a recent scientific article published in eLife, Predoctoral Researcher José Fabricio Hernández López from the Graduate School of the Stowers Institute (GSSIMR) and coauthors describe their latest research to identify rules that govern the spread of certain “selfish” genes, which, as their name indicates, are selfish in their behavior and stack the odds of their own transmission to the next generation in their favor. Selfish genes are considered parasites of the genome because they do nothing to promote the overall fitness of the organism and sometimes even cause problems such as infertility.

When organisms make reproductive cells like eggs or sperm, normally only one of two gene copies at a given site is distributed to each reproductive cell. This process, known as Mendel’s law of segregation, serves to maintain genome size in their offspring, who get half of their genes from each parent. But sometimes laws are broken. And some of the violators of the segregation law are selfish genes, which are found in many living organisms, from single-cell yeast to humans.

In the lab of Associate Investigator and GSSIMR Vice Dean Sarah Zanders, PhD, Hernández López and collaborators studied aspects of selfish gene transmission in the yeast S. pombe. Although seemingly simple, yeast cells can exhibit different mating behaviors. Instead of eggs and sperm, their reproductive cells are spores. The researchers examined how patterns of outcrossing, or mating between individuals of distinct lineages, and inbreeding affected the spread of selfish genes.