College entrance examination resource network (ks5u.com) The expert hypothesis of college entrance examination around you-deductive hypothesis deductive method After asking questions on the basis of observation and analysis, put forward the hypothesis to explain the problem through reasoning and imagination, deductive reasoning according to the hypothesis, and then test the conclusion of deductive reasoning through experiments. If the experimental results are consistent with the expected conclusions, the hypothesis is proved to be correct, otherwise, the hypothesis is wrong. This is a scientific method commonly used in modern scientific research, called hypothesis-deduction method. An example of hypothetical deduction is 1, Mendel's pea hybridization experiment. /kloc-In the middle of the 9th century, Mendel did a lot of hybridization experiments with peas. In the process of observing, recording and analyzing the experimental results, it was found that some comparative characters were separated from the hybrid offspring, and the second generation appeared free combinations of different characters in two or more pairs of relative characters hybridization experiments. He put forward a hypothesis through rigorous reasoning and bold imagination, trying to explain the phenomenon of personality separation and free combination of different characters. Then he cleverly designed a cross-test experiment to test the hypothesis. It is impossible to directly verify the hypothesis itself, but to verify the inference derived from the hypothesis, that is, if the hypothesis that genetic factors determine biological characteristics is established, then the results of the test experiment can be deduced and predicted theoretically according to the hypothesis; Then, the data obtained from the empirical test are compared with the theoretical derivation. If they are consistent, the assumption is correct; If they don't agree, the assumption is wrong. Of course, the actual test process of hypothesis is very complicated, and it is impossible to explain the problem by one or two experiments alone. In fact, many experiments conducted by Mendel have obtained similar results. Later, several scientists made many observations similar to Mendel's experiment. After a large number of experiments verified the authenticity of Mendel hypothesis, Mendel hypothesis finally developed into a classic theory of genetics. As we know, deductive reasoning is an important form of reasoning in scientific argumentation. Why can the consistency between experimental values and theoretical deduction prove the correctness of the hypothesis? Facts have proved that the phenotype and proportion of the offspring of test cross truly reflect the type and proportion of gametes produced by the offspring. According to the gametes of the offspring, the genetic composition can be inferred, and revealing this mystery plays an important role in the process of deductive reasoning. Without revealing this mystery, it is difficult for students to understand the scientificity and rigor of "hypothesis-deduction method", and the conclusion drawn by deductive reasoning is still in ignorance. 2. 1900, three scientists rediscovered Mendel's work respectively, and the genetics community began to realize the significance of Mendel's genetic theory. If Mendel's supposed genetic factor, the gene, does exist, then where is it? 1903, American geneticist Sutton found that the segregation of alleles, a pair of genetic factors assumed by Mendel, was very similar to the segregation of homologous chromosomes in meiosis. According to the obvious parallel relationship between genes and chromosome behavior, Sutton put forward the hypothesis that genes are carried from parents to offspring by chromosomes, that is, genes are located on chromosomes. Morgan, an American geneticist, has made it clear that he doesn't believe Mendel's genetic theory, and he also doubts the hypothesis of Sutton, a college entrance examination expert around you. Later, he did many fruit fly hybridization experiments and linked a specific gene with a specific chromophore -X chromosome, thus confirming Sutton's hypothesis. It can be seen that the process of exploring the relationship between genes and chromosomes is also a hypothetical-deductive process. 3. The presentation and confirmation of 3.DNA replication model and the whole central principle are all cases of "hypothesis-deduction method". Take the clarification of DNA molecular replication mode as an example. Watson, an American biologist, and Crick, a British physicist, wrote at the end of their famous paper on the double helix structure of DNA molecules: "After putting forward the viewpoint of base-specific pairing, we immediately put forward a possible mechanism of genetic material replication." They immediately published the second paper and put forward the hypothesis that genetic material replicates itself: when DNA molecules replicate, the double helix is untied, and the two single strands that have been untied are used as templates respectively to form new strands according to the principle of base complementary pairing, so each new DNA molecule retains one strand of the original DNA molecule. This method of replication is called semiconservative replication. 1958, scientists used Escherichia coli as experimental materials and designed ingenious experiments with isotope labeling method. The experimental results are consistent with the expected phenomenon deduced from the hypothesis 1, which confirms that DNA does replicate in a semi-reserved way. 4. The decoding of genetic code is another important event in the development of modern genetics after the model of DNA double helix structure was put forward. Since 1953 put forward the model of DNA double helix structure, scientists have launched a series of explorations around the decoding of genetic code. The idea that three bases encode 1 amino acid was put forward by American Soviet physicist Gamov. Crick and his colleagues studied the influence of the increase or decrease of gene base on protein encoded by T4 phage through a large number of experiments. The results showed that only three bases in the genetic code could encode 1 amino acid. But their experiments can't explain which amino acid the 1 code of the three bases corresponds to. Nirenberg and Matthew, two young American biologists, successfully decoded the genetic code of 1 by changing their design ideas and designing experiments skillfully. In the following six or seven years, scientists deciphered all the genetic codes and compiled a codon table. Copyright: College Entrance Examination Resource Network (www.ks5u.com)www.ks5u.com Copyright @ College Entrance Examination Resource Network.