How Mendel unlocked the secrets of heredity

The German newspaper Deutsche Zeitgeist published an article entitled "The World's First Geneticist" by Tina Bayer on July 20. The full article is excerpted below.

How do brown-haired parents have blond children? Gregory Mendel was the first to understand this and many other things, and he was a multifaceted genius who had been underestimated all his life.

Scientific pioneer

Born in 1822 in Silesia (now the Czech Republic) in the Austrian Empire, Mendel - then known as Johann - entered the Augustinian monastery of St. Thomas in Brno at the age of 21, probably for one of the reasons that he had been living in dire straits. At the monastery, Mendel received the name Gregory, and the abbot encouraged him to continue to develop his scientific interests. Later, Mendel took charge of the monastery's gardens, where he conducted his famous pea hybridization experiments. When Mendel began his research, the concepts of "genetics" and "genes" did not yet exist. The structure of the genetic material DNA was only discovered about 100 years later by molecular biologists James Watson and Francis Crick, but Mendel was the one who discovered that there must be a carrier material for genetic information in living cells.

Plant breeders

To study how traits are inherited, Mendel originally wanted to breed mice. But since that involved mating, the bishop would not allow him to conduct such an experiment. So Mendel began crossing peas in the monastery's garden. He found that if he crossed purple-flowered peas with white-flowered peas, all the offspring would have purple flowers. If the second generation of purple-flowered peas were allowed to cross themselves, some of the resulting offspring would again have white flowers. Before Mendel's discovery, it was widely believed that heredity always mixed the characteristics of the parents. The maxim of the time was that if a giraffe mated with a short-necked deer, its offspring would have medium-length necks. This is also the case for many heredity, and transferred to the color of pea flowers is that the offspring of a cross between a white-flowered pea and a purple-flowered pea should have pink flowers. Mendel understood why this was not the case with peas, because the characteristics were inherited as complete units, as if the father and mother had passed on pearls to their children. Today we know that these "pearls" are genes. Genes that affect the same trait (such as hair color) but cause different characteristics (blond or brown) are called alleles.

Creation of genetics

Mendel also discovered that "pearls" - i.e., genes - do not affect the appearance of an organism to the same degree. He explained this by saying that his peas inherited the information to produce purple flowers (alleles) from one parent in the first cross experiment and white flowers from the other, but both produced purple flowers. Mendel described the purple-flowering allele as dominant and the white-flowering allele as recessive. Seedlings only produce white-flowered peas if they inherit the information about white flowers from both the mother and the father. This explains why in the second cross with purple-flowered peas, some plants suddenly had white flowers again, and the ratio of purple to white flowers was 3:1. In the white-flowered plants, both pea parents passed on their inactive white-flowered alleles to the next generation. The understanding that dominant and recessive genes lead to dominant and recessive inheritance of traits is one of the foundations of modern genetics. It applies not only to peas but also to most organisms, including humans. However, some traits can be mixed in the offspring. The flower color of pink pea flowers is an example of this intermediate type of inheritance.

Statistical mathematicians

Mendel's idea of using mathematics to understand the vibrant nature was also new. He compensated for the uncertainty by using the "law of large numbers" - which one might talk about today as statistics. Thus, Mendel studied a large number of plants: between 1856 and 1863, he reportedly grew about 28,000 peas and studied 40,000 flowers and 400,000 pea grains. He found that genetic traits are, on average, passed from parent to offspring according to mathematically precise ratios. Because Mendel's results were so definitive, he was accused several times after his death of falsifying them. But that suspicion has now been put to rest.

Meteorological researcher

As a scientist, Mendel didn't just focus on plants. He was also a meteorologist and a beekeeper. In the garden of his monastery, he built an apiary where light-colored queens mated with dark-colored males. He wanted to show that the rules of heredity he described also applied to the animal kingdom. As a meteorologist, he set up a measuring station in the monastery and published nine professional articles. The paper entitled "The Tornado of October 13, 1870" has also survived, the first description of a tornado in the history of the Brno region.

Minimalist

Why Mendel received so little attention during his life is not entirely clear. His personality may have played a role: Mendel was considered shy by nature and did not pass any official exams for unknown reasons. One might assume that he was not a man who pushed himself to the forefront. Perhaps he was also overshadowed at the time by Charles Darwin, whose theory of evolution had shaken up the worldview of the time a few years before Mendel published his findings.

Mendel was able to discern the rules in the genetic maze because of his idea of not looking at the overall appearance of the object of study, but rather focusing on a particular trait. One trait was the color of the flower, and another was the shape of the pea, which he classified as "round" or "wrinkled". He also eventually realized that traits are usually inherited independently of each other. Today, it is known that this happens when genes are located on different chromosomes.

Genius is underestimated

None of Mendel's contemporaries recognized the impact of his findings. He published them in 1866 in the little-known professional journal of the Brno Society for Natural Research under the modest title "Experiments on Plant Hybridization". Mendel did try to draw attention to himself and his work: he sent more than a dozen copies of his papers to prominent scientists but in vain. It was not until 1900, 16 years after Mendel's death in 1884, that the botanists Hugo ed Tries, Carl Collins, and Erich Carmaker independently carried out the experiments Mendel had done and came up with very similar results. It was at this point that the results of the Augustinian monk's work were recognized by many scientists.