Trait inheritance study challenges the simplicity of genes acting alone
Natural populations – such as groups of animals, plants or even humans – show an astonishing variety in their traits. These traits include physical characteristics, how their bodies function, how they behave and even how susceptible they are to diseases. A big goal in biology is to figure out what specific genes cause these differences. However, this is more complex than it sounds. Traits are not just influenced by genes but are also shaped by non-genetic factors such as the environment and epigenetics (chemical changes that affect how genes work without altering the DNA itself). Even when focusing solely on the genetic side, research still struggles to determine all genetic factors behind complex traits.
Why traits are hard to predict
This is known as the ‘missing heritability’ problem. When scientists study families, they can estimate how much of a trait is inherited. But when they look for the specific genetic variants responsible – even when using tools like large-scale genome-wide association studies – they can only explain a small fraction of that heritability. The reason for this lies in genetics complexity. According to Joseph Schacherer, coordinator of the EU-funded project PhenomeNal, many factors are being overlooked. These include rare genetic variants that, while uncommon, can have a profound impact or interactions among genes (epistasis) – where the effect of one gene depends on the activity of others. Another factor is related to differences in how genes are expressed, meaning the same gene might behave differently depending on the individual. “We revealed that traits are not just influenced by individual genes but are shaped by complex interactions, rare variants and the broader genetic background,” notes Schacherer. “Even seemingly simple traits can vary widely across individuals owing to hidden factors such as epistasis and expressivity – how strongly a gene is expressed.” These findings challenge the traditional view that traits follow predictable genetic rules and help explain why many traits in humans and other organisms are hard to map or predict.
Baker’s yeast as a window to decode genetic complexity
For their study, researchers focused on Saccharomyces cerevisiae – or baker’s yeast. Its genome is simple, fast-growing and easy to manipulate, making it ideal for research. Unlike humans or other complex organisms, baker’s yeast thrives in tightly controlled environments, while its rich genetic diversity is captured in thousands of natural isolates. Furthermore, it shares similar biological processes with humans, making it a valuable system for uncovering universal genetic principles. “By crossing different yeast isolates and analysing how their traits are passed down, we revealed how genetic differences, rare mutations and complex gene interactions influence growth, stress resistance and survival,” states Schacherer. With powerful tools such as genome sequencing, high-speed robots and gene editing, the goal was to create a complete picture of how traits emerge from genetic variation. “Functional tests using allele libraries and CRISPR(opens in new window) editing showed how a strain’s genetic makeup affects the impact of specific genes. Moreover, transposon mutagenesis(opens in new window) identified genes essential in specific contexts, offering a genome-wide view of gene expression and the stability of biological pathways,” adds Schacherer. With European Research Council support, the project’s work is proving crucial for advancing genetics, improving trait prediction and informing fields such as personalised medicine and evolutionary biology.
