Human beings use the principle of genetic variation to breed new varieties in the following ways.

Case 1: The principle of eugenics. To put it more clearly, it is to select good individuals in good groups for reproduction, so that good traits (in this case, milk-producing genes) are better consolidated and developed.

Case 2: Hybrid dominance. Genes are present in pairs and are generally divided into dominant and recessive genes.

High yield and low yield belong to a pair of genes, and high yield is dominant relative to low yield. In the same way, lodging resistance and lodging are a pair of genes, and lodging resistance is dominant relative to lodging. Pairs of genes, if one is dominant and the other is recessive, then the offspring will exhibit dominance. In this example, the offspring produced by crossing high-yielding lodging wheat with low-yielding to floating wheat will show the dominant genes of both parents, i.e., high-yielding and lodging-resistant traits, which are high-yielding and lodging-resistant wheat.

Case 3: Chromosome inheritance and variation. The traits of ordinary green peppers (that is, what we see) will not change in the general environment, so the green peppers we see are similar, no different.

When the external environment changes, that is, it is carried to outer space as mentioned in this example, then it will be affected by the cosmic environment, such as temperature, air, cosmic rays and other factors, and its genetic factors may change. When these seeds are brought back to Earth and planted, the green peppers that grow will undergo certain changes, maybe in color, maybe in taste, and so on. These special green peppers are selected and cultivated, and then space green peppers with certain characteristics are formed.

It's quite verbose, I don't know if I'm satisfied!

Artificial selection for genetic recombination genes chromosomal mutations.

Test question analysis: there are many ways to use the principle of genetic variation to cultivate new varieties, human beings use genetic recombination, gene mutation, chromosome variation and other heritable variations to cultivate new biological varieties, such as cultivated hybrid rice is the use of wild rice and cultivated rice gene combination to breed new varieties, cultivate artificial hybrid rice, is not only artificial breeding, but also belongs to hybrid breeding, irradiation of wheat seeds with a certain dose of radioactive cobalt, belongs to the process of using radiation to induce genetic mutations and produce heritable variation, It is a genus of mutagenesis breeding.

The main methods of human beings to breed new varieties using the principle of genetic variation are:

The first is to use the principle of gene mutation to breed high-yield penicillin.

varieties, space peppers, etc.;

The second is the use of genetic recombination.

principle, to breed mixed old bond rice.

new varieties such as hybrid corn;

The third is to use the principle of chromosomal mutation to breed new varieties such as childless watermelon.

Therefore, the answer is: high-yielding penicillin varieties; Space Pepper; Hybrid rice (reasonable is enough).

Human beings use genetic recombination, gene mutation, chromosomal variation and other heritable variations to breed new biological varieties For example, Yuan Longping's hybrid rice variety "Indica 9311" is a new rice variety obtained through hybridization, which is a genetic recombination that controls different traits; Irradiation of wheat seeds with a certain dose of radioactive cobalt belongs to the process of using radiation to induce genetic mutations and produce heritable variations, so the process of cultivating new wheat varieties by this method belongs to genetic mutations. The triploid seedless watermelon is treated with colchicine in the seedling stage with ordinary watermelon to obtain tetraploid watermelon, the tetraploid is used as the female parent, and the ordinary watermelon is the paternal parent, and the triploid watermelon is produced by crossing; It belongs to chromosomal variations

So the answer is:; hybrid rice; mutagenesis breeding, etc

There are many ways to use the principle of genetic variation to breed new varieties, and humans use genetic recombination, gene mutation, chromosomal variation and other heritable variations to cultivate new biological varieties. Irradiation of wheat seeds with a certain dose of radioactive cobalt belongs to the process of using radiation to induce genetic mutations and produce heritable mutations, which belongs to mutagenesis breeding.

Therefore, the answer is: artificial breeding; cross-breeding; Mutagenesis breeding

a. It is a favorable variation in the artificial selection of dairy cows, and the milk yield is high, which belongs to selective breeding, so this option does not meet the theme;

b. It is the use of space rays to induce mutation of ordinary bell pepper seeds, which belongs to mutagenesis breeding, so this option does not meet the topic;

c. It is the use of the transmission of genes between parents and children to recombine genes to produce stable, hereditary, and new varieties with excellent traits, which belongs to hybrid breeding, so this option is in line with the topic;

d. It is a variation in the size of peanuts caused by changing the environment, so this option does not meet the meaning of the topic, so choose C

There are many ways to use the principle of genetic variation to breed new breeds, and humans use genetic recombination, gene mutation, chromosomal variation and other heritable variations to breed new biological varieties such as artificial selection breeding, from different milk cows, after selection, to breed high-yielding dairy cows Therefore, the answer is: artificial selection breeding

There are many ways to use the principle of genetic variation to breed new varieties, and human beings use genetic recombination, gene mutation, chromosomal variation and other heritable variations to breed new biological varieties such as cultivated hybrid rice is a new variety cultivated by using the genetic combination of wild rice and cultivated rice, and artificial hybrid rice is cultivated, which is not only artificial breeding, but also hybrid breeding; Irradiation of wheat seeds with a certain dose of radioactive cobalt belongs to the process of using radiation to induce genetic mutations and produce heritable variations, which belongs to mutagenesis breeding.

Therefore, the answer is: artificial breeding; cross-breeding; Mutagenesis breeding

artificial breeding; cross-breeding; Mutagenesis breeding

Test question analysis: artificial selection of favorable variation, belongs to selective breeding, the use of gene transmission between parent-child generations, so that the gene recombination, to produce stable, hereditary, with excellent traits of new varieties, belongs to hybrid breeding, the use of space rays to induce the mutation of ordinary bell pepper seeds, belongs to mutagenesis breeding, these are the methods of cultivating new varieties.