The Hindu Business Line : Teacher, preacher and geneticist

HEREDITY matters. If it were not so, there would be no arranged marriages, no patricians and plebeians, no apartheid and no ethnic cleansing. While others were debating how traits were inherited, some arguing that the father was the sole donor and the others rooting for the mother as the giver, it was heredity which fascinated the 19th century Moravian priest John Gregor Mendel. Till then, no one was sure how animals or plants passed down traits. And even Darwin knew that the lack of an explanation for heredity left a big gap in his theory of natural selection.

In one of the great triumphs of scientific experimentation, the Austrian biologist and monk John Gregor Mendel, Darwin's contemporary, solved this problem in the mid-19th century. His discovery is as pivotal to genetics as Darwin's is to evolution. Truly, it has been said that the modern age of genetics was born with Mendel. Ironically, Darwin never found out. The results of Mendel's carefully designed and meticulously executed experiments, which involved nearly 30,000 pea plants followed over eight generations, were ignored until long after both he and Darwin were dead.

Mendel was born in 1822 on July 22, in Hynicice, near Brno in Czeh Republic in a rich peasant's family. John, or more appropriately Johann, went to school at Opava 20 miles away from home. When he was 16, his father became disabled, being seriously injured in the forest, and fell sick for prolonged periods. Therefore, only at 19 he joined the Philosophy Institute at Olomouc. He was plagued by family problems till his brother-in-law set aside an allowance on condition that he became a priest. Since Mendel did mathematics and physics impressively, his physics teacher recommended him to the monastery in Brno where he became a novitiate, taking the middle name Gregor in 1843 under Abbot Napp. Napp was an enthusiastic plant breeder and played a significant role in shaping the future geneticist; the term "gene" and its derivatives were unknown then. Fortunately for the future of science, Napp ignored his disciple's laxity in religious matters while leaving him alone to pursue his interest in gardening and plant hybridisation. The monastery did help him and yet his burning ambition was to be a teacher. Napp also helped Mendel to become a school teacher, teaching seventh graders mathematics and physics. At 29, Mendel enrolled himself at the University of Vienna where he came under the influence of Doppler, the famous physicist whose discovery, helped in determining velocities of moving objects. Largely because of this and his own flair for mathematics, Mendel succeeded in making sense of heredity as he brought the precision of mathematics and physics to the subject. While Darwin was fascinated by the diversity in nature, Mendel chose to explore the existence of a fundamental order.

Mendel finished his education in Vienna in 1853 and probably began his experiments with peas. During the period he also taught physics and natural science. Threat to his seminal effort came in the form of likely closure of the monastery on grounds of deviating from the main vocation of religion to teaching modern science. But his mentor Napp was able to avert it by his persuasive methods with his archbishop.

In the mid-19th century it was not entirely clear that both parents contributed to the offspring, and it was still not accepted that plants were sexual beings at all. The spermatists maintained that the plant embryo arose from the pollen tube and the female cells merely provided the nourishment.

There were ovists who averred with matching vehemence that the egg from the mother provided all he nourishment and the sperm merely triggered development. Mendel, of course, maintained that both parents contributed equally and backed his hypothesis with experiments on peas in the definitive paper published in 1866, after 12 years of research.

He studied peas because he knew, of all plants, they were most likely to give the clearest and most informative results. He also knew the weakness of his approach; it cannot be assumed that rules discovered in simple cases can necessarily be applied across the board. He looked at 17 other species and took up a study of bees. He wasted many years studying hawkweed, mostly prodded by the reputed Swiss botanist, Carl Naegeli, and did not meet with any success as the plant, like some other members of the daisy family, is parthenogenic, that is, the next generation arises from an unfertilised egg and only the female traits are passed on to the offspring. Scientists feel he could have accomplished more had he not deferred to Naegeli under the rigid hierarchical system, among scientists. Today, such a thing cannot happen as young researchers would fight their corner.

The patient monk carefully bred and cross-bred pea plants to see how a few specific traits — height was one — were passed down. When Mendel bred a tall plant to a short one, all of the offspring were always tall, never blending to medium size. When he then bred those offspring together, three out of four of their offspring were tall, but one was short. Mendel knew exactly what this meant. Height was passed down in a `particle' we now call a gene (though Mendel never used that term himself). A plant was short or tall depending on the random combination of genes it inherited.

However, even as Mendel was engaged in his research, Darwin, like many of his contemporaries, speculated that characteristics of the parents were blended — like mixing paint — as they passed to the offspring.

But if that were true, some of Darwin's critics pointed out, then how could a single fortunate mutation be spread through a species? It would be blended out, just as a single drop of white paint would be in a gallon of black. Mendel read Darwin with deep interest, but he disagreed with the blending notion, hypothesising instead that traits, such as eye colour or height or flower hues, were carried by tiny particles that were inherited whole in the next generation.

So an adaptive mutation could spread slowly through a species and never be blended out. Darwin's theory of natural selection, building on small mutations, could work. But no one at the time understood the implications of Mendel's experiments. He soon left biology to focus on running his monastery.

Mendel was rediscovered only in 1900, 16 years after his death. The man who did most to restore the world's knowledge of Mendel, was his biographer Iltis. Only then did Mendel, who did not pass his teacher's exams and who did not get a doctorate — working without a microscope, without computers, but with a thoughtful hypothesis, a carefully designed experiment, and enormous patience — receive the credit for one of the great discoveries in the history of science.

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Teacher, preacher and geneticist