What is the matter of backcrossing, why do humans let animals backcross?

2021-01-04 | Zhong Ming talks about science Original |

Backcrossing is one of the breeding methods commonly used by breeders. Using this method, breeders have cultivated many excellent livestock varieties and plant varieties, such as: backcrossing Sanyuan pigs and Yangmai 18 wheat varieties. If notThe method of backcrossing may make it difficult to cultivate some excellent livestock or crop varieties, which is very unfavorable for agricultural development.

But on the other hand, backcrossing often involves ethics and morality. For example, it is said that Fu Yanqing in the Northern Song Dynasty likes to raise horses. In order to cultivate good horse breeds, he let a small horse backcross with a mare. But this story was taken by others.I see, because our country attaches great importance to ethics and morality, people are puzzled by this behavior and say: It is rude to call animals and beasts, so father and son get together!

Because backcrossing challenges human ethics and people in the past did not understand the laws of biological genetics, so in the past, people rarely used backcrossing to breed. Until Mendel unlocked the laws of biological genetics, breedingThe teachers only began to try to use backcross as a breeding method.

However, the problem also arises. Backcrossing is a kind of inbreeding. We know that inbreeding is harmful to organisms. Does backcrossing breeding cause serious harm to organisms? Does backcrossing challenge the ethics of animals?

Back hand

For animals, they will try to avoid inbreeding and backcrossing. For example, although koalas move slowly, male koalas will go to farther places to establish habitats. This is because female koalas willThe opposite sex develops a good impression and breeds offspring. When the male lion grows up, he will leave his own population and challenge other lion kings to obtain mating rights.

Male spotted hyena cubs have a very high status in the population, but after joining other populations, their status will drop to the lowest level. Even so, they will still leave their own population because females in their own population will not mate with themselves.

For plants, although they will also avoid marriage between close relatives, for example: some plants will produce delicious fruits, lure animals to eat them, and then bring their seeds to distant places. But plants do not exclude backcrossing andInbreeding, such as: peas can only be reproduced by selfing, and apple flowers will also be stained with the stamens of another flower.

The reason for this is that plants cannot leave their own land, which makes them prone to inbreeding and even backcrossing. However, since plants have no pain nerves, even backcrossing will not cause a decline in the quality of life. At most, they will appear.Some unfavorable evolutions, such as: poor disease resistance, slow growth, etc. These undesirable traits are sometimes eliminated under natural selection.

That is to say, backcrossing is not harmful to plants, but for animals, backcrossing can sometimes cause serious pain to them. The most typical one is Canadian hairless cats.

Canadian hairless cat is a breeder who observes that a litter of kittens born by her own mother has sparse hair. She immediately realized that this can be cultivated into a new breed, so that those who are allergic to cat hair can also raise it.Therefore, she selected the kittens with the sparsest hairs from the kittens and backcrossed them with the female cats, and obtained hairless cats. However, hairless cats carry many genetic diseases, which cause inconvenience to the normal life of cats. The Cat Association even refused to admit this.Breeding cat breeds. Later, cat lovers carried out cross-modified genes for the cat, and then turned it back into a hairless cat through a series of methods, which improved the quality of life of hairless cats. This breed was also recognized by the Cat Association.

Since backcrossing will cause inconvenience to animal life, why is there no problem when using backcrossing in livestock breeding?

Livestock breeding

The difference between livestock breeding and pet breeding is that livestock breeding must consider whether the breed can resist diseases and whether other physical traits can meet people's requirements for livestock.

That is to say, when breeding new varieties, the breeder will first consider whether the individual is healthy. If there is a serious genetic disease, the individual will be eliminated. Although backcrossing will cause recessive pathogenic genes to be revealed in the offspringHowever, there will be some healthy individuals that meet people's breeding requirements. Breeders will select these healthy individuals. If these healthy individuals can still meet people's needs for livestock, such as: high yield, good disease resistance,Then the individual will be retained and reproduced from generation to generation.

To some extent, breeders act as natural selection to eliminate individuals with poor genes. Therefore, even if breeders use backcrossing techniques, the new breeds they produce are still healthy.

Of course, if you want to ask whether the backend will involve ethics, we can only say that ethics is a concept in the human world, and animals will not follow it, but they will try to avoid this phenomenon.

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