Mendel chose pea for genetic experiment. The specific reasons are as follows: Mendel found that pea is a closed-pollinated plant. Because of long-term closed pollination, the purity of pea is guaranteed. That is to say, the offspring of a pea variety with red flowers will also bloom, and the offspring of a tall pea will never be short; In peas, red flowers and white flowers, high and short, round and wrinkled lines are so distinct. These different pea colors and grain shapes are called relative traits. It is precisely because the genetic relative traits of pea are distinct, and the characteristics of closed pollination make its genetic relative traits very stable. When studying plants with this characteristic, it is easy to observe the influence of heterogeneous pollen. Although pea is a closed-flowered plant, its flower shape is relatively large. It is easy to remove stamens from pea flowers by artificial means and send pollen to female flowers. Mendel confidently started a genetic experiment that had never been carried out before. He carefully picked the male flowers of red peas and sent the pollen of white peas to get the hybrid generation (F). Peas grown from the first generation seeds are red flowers, so that the first generation peas are pollinated and the second generation seeds are obtained. When the plants grown from the second generation seeds bloom, 3/4 are white flowers, and 1/4 are white flowers. He called the parental traits that appeared in the first generation as dominant traits, and the parental traits that did not appear as recessive traits. The phenomenon that the characters of two parents appear at the same time in the second generation is called "separation phenomenon". When Mendel made a hybridization experiment with peas, he carefully observed the following seven pairs of completely different characters:

Color of flowers: red and white;

Seed shape: round and wrinkled;

Color of leaves: yellow and green;

Flowering position: axillary (that is, branched) terminal;

The shape of mature pods: full and shrinking;

Height of plants: height and height. The initial experiment was to cross two peas (parents) with obvious differences in the above single traits, and the above seven groups of related traits were crossed seven times respectively. The results of seven crosses were surprisingly consistent. That is, the hybrid generation has only one parental trait. For example, when a plant with red flowers crosses a plant with white flowers, the hybrid offspring always have the same red flowers. Peas with yellow cotyledons are crossed with peas with green cotyledons, and the first generation (F) always has the characteristics of yellow cotyledons. The phenomenon that only one parent of this hybrid appears in the first generation is no exception in the hybridization of 7 pairs of relative traits observed by Mendel. In addition, when the first hybrid is self-pollinated, the seeds of the second hybrid are obtained. In the second generation of seven hybrids, the characters of two hybrid parents appeared, that is, they all separated. More interestingly, in the second generation of hybrid, the traits that parents appeared in the first generation (dominant traits) and the traits that parents did not appear in the first generation (recessive traits) were both 3: 1.

1866, Mendel published the paper "Plant Hybridization Experiment", which revealed the genetic law of separation and free combination of biological characters. Later, people called his discovery "Mendel's first law" and "Mendel's second law" respectively.

However, this epoch-making paper still did not cause any repercussions at that time. There are three reasons for this:

First, Darwin's masterpiece The Origin of Species was published in 1859, before Mendel's paper was published. This book has aroused the interest of the scientific community, and almost all biologists have turned to the discussion of biological evolution, thus ignoring the attention to Mendel's papers.

Second, the scientific community at that time lacked the ideological basis for understanding Mendel's law. First of all, the scientific thought of that era did not include the proposition put forward by Mendel's paper: heredity is not the whole picture of an individual, but personality. Secondly, the expression of Mendel's thesis is brand-new. He combined biology with statistics and mathematics, making it difficult for contemporary naturalists to understand the true meaning of the paper.

Third, some authorities, out of prejudice or incomprehension, regard Mendel's research as a general hybridization experiment, which is not much different from what others have done.

In his later years, Mendel confidently said to his good friend Geser, a professor of geodesy at Bruen Institute of Advanced Technology, "Look, my time has come." This sentence became a great prophecy. It was not until Mendel's death 16, 34 years after the pea experiment paper was officially published, and 43 years after the pea experiment, the prediction became a reality.

It was not until 1900 that it was confirmed by Defrees in the Netherlands, Clarence in Germany and Chuschemark in Austria in their respective pea hybridization experiments, thus opening the curtain of modern genetics. Mendel is therefore known as the real founder of genetics and the "father of modern genetics".