Belgium
July 20, 2022
In 1822, Gregor Mendel - the founding father of genetics – was born. In 1866, he published “Experiments on plant hybrids”, a 40-pager in which he describes the transmission of characteristics in pea to their progeny. Little did he know that it would become the foundation of modern genetics. In the early 1900s, after his death in 1884, his findings were rediscovered and Mendel’s Laws of Inheritance grew into the basis of modern biology. To celebrate his 200th birthday we look back and ahead together with VIB scientists Ive De Smet, Joren De Ryck, and Matilde Sanches from the VIB-UGent Center for Plant Systems Biology, and Seppe De Winter from the VIB-KU Leuven Center for Brain & Disease Research.
Historical background
Gregor Mendel grew up in a supportive farmer’s family, which allowed him to pursue higher education. Unfortunately, financial problems prevented him from completing his philosophy studies at the University of Olmütz. So, he decided to become a monk to pay for his education. His eagerness to learn, together with his interest in plant cultivation methods, led him to study hybridization in garden pea in the monastery in Brno (Czech Republic). He chose the humble pea because the plants are easy to grow, generate plenty of offspring, and possess a variety of observable features.
During his experiments, he crossed around 28.000 plants. A meticulous job where the male flower has to be removed by scissors from the female parent plant – to prevent self-pollination – and pollen from the desired male parent plant has to be subsequently applied using a tiny brush. From his observations, he deduced that plant characteristics are transmitted to their progeny independently, as single ‘factors’, following a certain ratio with some traits having a higher chance of being inherited – introducing the terms dominant and recessive traits.
When he published his findings in 1866, it had little impact. It was only after his death that the importance of Mendel’s work became apparent. In 1900, Hugo De Vries, Carl Correns, and Erich von Tschermak reproduced the work of Gregor Mendel independently from each other, which led to the formulation and popularization of Mendel’s Laws of inheritance. Finally, Ronald Fisher combined Mendelian genetics with Darwin’s theory of natural selection and wrote ‘The genetical theory of natural selection’ in 1930 – a turning point for evolutionary biology that continues to resonate in today’s researchers.
Mendel and Darwin were performing ground-breaking genetics experiments in parallel. What if they would have collaborated?
Ive: “Actually, Mendel was aware of Darwin’s work, but Darwin knew nothing about Mendel’s activities. And that while Mendel clearly filled a gap in Darwin’s theory, namely a lack of explanation for heredity.”
Joren: “Zeitgeist is an important aspect here. Mendel’s observations were in contrast to the conventional theory at that time: blending inheritance – the idea that the progeny receives an ‘average’ of the parent’s traits. Charles Darwin mentioned he had doubts concerning the blending theory and even conducted experiments with pea plants, very similar to those of Mendel. Darwin crossed two pea parent plants with very different colors and noticed that the offspring had either the color of the first parent or the second parent, but never a mix (blend) of the two. These findings further supported Darwin’s theory of evolution because blending inheritance would mean that beneficial traits would have blended away long before natural selection could occur. “
Ive: “They were both great minds, with an amazing sense of observation leading to stunning conclusions. They were both working on genetics but were still missing some knowledge – not in the least about DNA and its importance. Mendel and Darwin could probably have made bigger leaps if they would have interacted, much like Wallace pushing Darwin to publish his conclusions.”
Joren: “Imagine Darwin’s travels had led him to the Czech Republic and, in a tavern somewhere, he had heard about the crazy experiments a certain abbot named Mendel was doing in the abbey of Saint Thomas. Surely, Darwin would have been intrigued and wanted to meet Mendel to discuss his own observations in pea plants. Mendel, who was also an enthusiastic beekeeper, would have been fascinated by Darwin’s exploration of the Galápagos Islands. Together they would conclude that, just like plants, animals and even humans followed the same laws of inheritance, and they could have come up with the term ‘genetics’ much sooner.”
Sounds like a science cafe in the old days! Would their encounter in the 19th century have an impact on our lives today?
Joren: “Whether the meeting between these two biologists would have affected our daily lives is uncertain, but we can be sure that Mendel’s findings would have gotten the appreciation they deserved much sooner. It was only in the 1930s and 1940s that Mendelian genetics was combined with Darwin’s theory of natural selection, leading to evolutionary biology as we know it today. Their hypothetical meetup would have certainly accelerated the field of evolutionary biology.”
Ive: “Building on that, with the knowledge we have gained and continue to gain, synthetic biology will revolutionize genetics. With the challenges humanity is facing – climate change and food security to name some – developing plants that can accommodate our needs going beyond classical genetics and breeding will become increasingly important.”
Matilde: “I can relate to what Ive is saying. Expanding the plant’s potential to cope with environmental stress becomes increasingly important. In contrast to Mendel, who studied the transfer of single genes, nowadays we need to take a broader, quantitative genetics approach. Characteristics such as abiotic stress tolerance are often determined not by one, but by many genomic regions. Indeed, we are currently using a genome-wide association approach to dig into water stress tolerance in grass pea, a close relative of the garden peas Mendel used!”
Geneticists today indeed have access to an extensive toolbox, including computational modeling and the introduction of mutations in their favorite model species, but Mendel studied the ‘natural way’ in which traits are transmitted to the next generation. Many traits are not inherited according to Mendel’s laws. Was he just lucky with his findings?
Joren: “Mendel chose seven traits of pea plants to investigate: plant height, flower position, flower color, pod shape and color, and seed shape and color – very visual and easy to compare. For sure, Mendel was lucky with these traits since they are located on one of the seven pea chromosomes, meaning their inheritance is also much simpler than when you have multiple copies of a gene.”
Ive: “Science is to a large extent based on luck in combination with smart choices and hard work. His choice to work with peas and his keen sense of observation – and the time he had as a monk – allowed him to formulate his laws. For example, the French botanist Antoine Duchesne (1747 – 1827) worked with strawberries, increasing the genetic complexity, and hence making him less known to a wider audience.”
Joren: “On some occasions, though, Mendel was much less lucky. For example, he tried to confirm his findings from the pea experiment in hawkweed but failed to reproduce the results as the first generation of hawkweed was very variable and many of their offspring were identical to the mother plant. Only later, it was found that hawkweed produces seeds through an asexual process, explaining Mendel’s struggle.”
Today, Mendel is omnipresent in biology and beyond. Even game developers find inspiration in his work. Seppe is one of the researchers at VIB that developed a genetics computer game called ‘Mendelcraft’.
Seppe: “Mendelcraft is a mod for Minecraft in which children can learn about Mendelian genetics while playing the game. The game contains chickens with varying features like feather color, size, and blood type. To examine how these features are inherited, players can perform several experiments. First of all, they can cross different chickens producing offspring showing new features. For example, crossing black and white chickens will only produce grey chickens. Crossing grey chickens with each other will produce 50% grey offspring and 25% black or white offspring, reminiscent of the pattern observed by Mendel.”
“Now we know that DNA is the carrier of those features and half of the DNA is inherited from each parent, resulting in specific patterns amongst offspring. In our lab (Lab of Computational Biology, Stein Aerts) we study how the genome encodes different neuronal cell types, so the topic is quite close to our hearts. In Mendelcraft, the DNA of the chickens can be examined by drawing blood which can be analyzed in the lab. By closely examining the DNA, the player will discover a link between the DNA sequence as seen in the lab, and the different features the chickens possess. Players can even take it one step further and modify the DNA to generate genetically engineered chickens displaying their features of choice. Using the correct combination of edits even a dinosaur can be created!”
Gamification is a great means of explaining complex theories and bringing them to the scientists of the future.
Seppe: ”Each year we organize a workshop on ‘Kinderuniversiteit’ (‘Kids University’) and ‘Dag van de Wetenschap’ (‘Day of Science’) in which children can explore genetics via Mendelcraft. This year, we – together with a computer science student Arne Loenders – updated Mendelcraft to the newest version of Minecraft and include the ability to support virtual reality. Mendelcraft can easily be installed at home and has an in-game manual/lab book. This allows children to enjoy the game beyond the workshops.”
“The experiments Mendel performed are, on the one hand, quite simple and can be easily simulated in a game but, on the other hand, very educational and elegant. By simply crossing differently colored chickens a child can learn the most fundamental aspects of biology.”
Mendelcraft can be downloaded and installed for free from curseForge (if you have a Minecraft account).
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