Mendel cultivated fruit trees with his father since childhood and was familiar with agronomy. 1840, he was admitted to the university, but dropped out of school because of his poor family. 1843 Joined Butian Palace and became a monk. The abbot of this monastery is the chairman of an agricultural association in a certain area of Austria. He advocated the use of courtyard clearing for agronomy experiments, and sent monks to teach in nearby schools, making the monastery an agronomy and education center in this area. Mendel once worked as an assistant to a very successful botanist here, so he was trained to engage in plant experiments. 1847 started to be a priest, 185 1 was recommended to Vienna university for further study. He studied mathematics, physics, chemistry, zoology, botany, entomology and paleontology, and learned the ideas and techniques of carrying out scientific experiments from famous teachers such as physicist Doppler and biologist Weng Ge. 1853, he returned to the monastery to continue as a priest, taught natural science courses in a technical middle school, and became an abbot in his later years. Although Mendel has been a priest all his life, he is undoubtedly an outstanding botanist because of his profound scientific literacy, superb experimental skills and excellent scientific research results.
Mendel saw an amazing regularity phenomenon in the previous work: when artificial hybridization is carried out between the same species, the same hybridization type always appears repeatedly. This aroused his keen interest. He spoke highly of the research achievements of many botanists, and pointed out their shortcomings: as far as the scale and methods of the experiment are concerned, a universal law that can clarify the restrictive relationship between parents and offspring in hybrid formation has not been effectively put forward. Mendel explicitly took seeking this universal law as his research goal. Because of his great breakthrough in experimental methods, after eight years of hard work, he finally achieved outstanding achievements.
Mendel's breakthrough and innovation in research methods are mainly manifested in two aspects: First, efforts are made to select suitable experimental materials. He pointed out: "The value and utility of any experiment depends on whether its materials are suitable for the purpose of research." Secondly, the factor analysis methods in non-life sciences such as physics, especially mathematical statistics, are cited. This was groundbreaking in biology at that time, so Mendel was considered as the founder of the practical application of mathematical thinking in biology.
In order to avoid suspicious or even absurd results in the experiment, he thinks that the plants used in the hybridization experiment must be: 1) stable and distinguishable; 2) the hybrid of this plant can prevent the influence of exotic pollen when flowering; 3) The fertility of hybrids and their offspring should not be obviously disturbed. According to his predecessors and his own experience, he first paid attention to leguminous plants. Through experiments, he found that peas have the above conditions, and peas also have the advantages of short growth period, easy cultivation, large flower organs and convenient emasculation and pollination during artificial hybridization.
1856, Mendel engaged in pea hybridization experiment on a piece of land in the monastery. Before that, he spent two years in seed selection and trial planting, and cultivated 22 pure varieties from 34 pea varieties for experiments to ensure the certainty of the experimental results.
When deploying the experiment, Mendel chose seven pairs of peas with obvious differences for experimental research: 1) the shape of the seeds is round or wrinkled; 2) The color of cotyledons, yellow or green; 3) The color of seed coat, gray or white; 4) the shape of the pod, full or wrinkled; 5) The color of the pod, yellow or green; 6) the position of the flower, the top of the main stem or the axis of the main stem; 7) The length of the stem, tall or short.
He crossed the purebred peas of each of seven pairs of traits, and their offspring plants, that is, their offspring, all showed the traits of a parent. For example, cross a pea with a tall stem and a pea with a short stem (with the tall stem as the male parent and the short stem as the female parent; Or take the short stem as the male parent and the tall stem as the female parent), and the offspring are all tall stems without short stems. Another example is the hybridization of pure peas with round grains and wrinkled grains (round grains are male parents and wrinkled grains are female parents; Or wrinkles are the father and round grains are the mother), and the descendants are round grains without wrinkles. Mendel called the traits that appeared in the first generation as dominant traits, and those that did not appear as recessive traits.
The first generation plants selfed to get the second generation. In the second generation of high-stem pea, about 3/4 are tall stems, 1/4 are short stems, and the ratio of plant height to plant height is close to 3: 1. In the second generation of pea self-crossing, about 3/4 were round grains and 1/4 were wrinkled grains, and their ratio was also close to 3: 1. In other cross experiments of several pairs of peas, the dominant and recessive ratio of the second generation is also close to 3: 1. This dominant and recessive trait appears in the second generation respectively, and has the regularity of stable proportion, which is called the separation phenomenon of genetics.
Mendel continued to cross two pairs of peas. For example, when peas with round seeds and yellow cotyledons are crossed with peas with wrinkled seeds and green cotyledons, the offspring all show the two dominant characters of round seeds and yellow cotyledons; The second generation is divided into round yellow, round green, wrinkled yellow and wrinkled green, and the number is 9/16: 3/16: 3/16:16, that is, 9: 3: 3. Any two pairs of pea hybridization experiments can obtain the same stable ratio. This law is called the law of free combination of genetics.
Mendel put forward the hypothesis of genetic factors to explain the experimental results. He believes that every character of plants comes from a pair of "genetic factors" in germ cells, one from the male parent and the other from the female parent. Dominant genetic factors that produce dominant traits are represented by capital letters a and b ... The recessive genetic factors that produce recessive traits are represented by lowercase letters a, b …. If the two factors are the same, it means a purebred with certain traits, such as a for tall stem traits, a for short stem traits, and AA for parent pure tall stem plants; The parent's pure dwarf plant is aa. He also assumed that each germ cell only got one of a pair of genetic factors. For example, there is only one A in the germ cell of tall pea, and only one A in the germ cell of short pea. After hybridization, two genetic factors combine to form Aa. A is dominant to A, so the offspring plants are all tall stems. When progeny pollinate themselves to form germ cells, A and A separate. Two kinds of sperm and two kinds of eggs containing A and A respectively combine to form the second generation, which has four factors: Aa, Aa, AA. The first three are dominant and the last one is recessive. The ratio of dominance to recessive is 3: 1.
Mendel wrote in his paper: "Let n represent the number of distinctive characters of two primitive species, 3n represent the number of items in the combination series, 4n represent the number of individuals belonging to this series, and 2n represents the number of combinations that remain stable." Some of the theoretical summaries are in good agreement with his experimental results.
Mendel's paper titled "Plant Hybridization Experiment" was published in Volume 4 of Journal of Butian Natural Science Research Society (1865) and sent to more than 20 libraries in Europe and America. He hopes that someone can do repeated experiments or controlled experiments, so that his conclusion can be tested. However, no one has done such a practical thing except being left out in the cold, being suspected and being laughed at. Thirty-five years later 1900, three botanists realized the important value of this paper and made it known to the world. This historical fact shows that Mendel's paper really has great vitality, and eight years of solid experimental work, a large number of real and reliable experimental data, exquisite and unique research methods and in-depth and reasonable theoretical analysis are its great vitality.