The selective breeding of animals has been practiced by humans for over 10,000 years. This involves choosing the best members of a particular species to breed with, then passing their genes onto the next generation. Over time, these genes or features can be used to improve the yield, efficiency, or any other benefit to farmers. Although we didn’t know this, artificial selection was discovered by scientists. The dairy cow is a great example. We have been selectively breeding them for about ten-and-a-half thousand years. We unknowingly increase the efficiency of their milk production and alter their biology to produce meat. We then domesticate it to allow it to be comfortable with humans. These effects have wider implications on the environment, ecosystem and the environment beyond the dairy cow.
Farmers began selective breeding cows when they caught and bred the Auroch, a species that has been extinct almost 400 years. It is probable that the Auroch were first used for their meat and milk. It is probable that only those who are calm and easy to farm will be able produce offspring. The only ones that were most suitable for either their environment or the purpose they were intended for in breeding them passed on their genes. This ensures that there will be a larger gene pool and a more efficient farming process. This is not a perfect system. Breeding a cow with a few favorable genes will ensure that they continue to be passed on. Its phenotype (or traits) may be beneficial, but its genes (or genotype) might not. If the positive genotype parent was heterozygous, which means it has a recessive genetic gene that is unfavourable, and the offspring are heterozygous, the chances of the unfavourable recessive recessive genes being expressed in the offspring, is high. This could be a cow with dwarfism or crookedtail syndrome. However, this is a common scenario. To ensure the best possible offspring, dairy and cattle farmers are able to breed two individuals who have the same gene. Test crosses are the most common way to identify an animal’s genotype. It involves crossing a single organism with another that exhibits the trait. The offspring from this cross can be used to determine if the first parent is dominant, or heterozygous. Another, more recent method is marker assisted selection, or “MAS”. This marks a particular gene and can be used to indirectly select for a genetic determinant. This is why MAS is a newer technique in selective breeding. Effectively using the MAS technique involves mapping the gene at the “quantitative-trait locus” or gene in question. This information is used to assist in marker selection. These genes can be linked or very close in order to mark the desired traits’ presence. Crossing can still occur between linked genes or very close genes. Thus, it is possible to use multiple markers to indicate its presence.
Because we kept the genes that we didn’t need or wanted out of the species, the genetic diversity of the cow has been decreasing since the first domestication. A biological implication is that it may not be possible to breed a gene out due to linked genes. Linked genes are genes that occur very close to each other on the samechromosome. This means they have a recombination probability of less 50%. Although a farmer might choose a cow with large muscles or a high milk production, there could be side effects such as fertility problems or immune system problems. Because they are all susceptible to the same disease, or all of them would die from it, the ecosystem could be negatively affected if all the cows are wiped out.
Cloning is another recent method that would allow the farmer to select individuals for a specific genotype to keep them in a certain way. They would have the ability to do this without going through the usual risk/ reward system. It’s easy to add additional genes to an individual or species. For example, cows can give their plasma to humans Citation. Transgenesis is a technique where genes from different species are inserted into another species’ genomes or used gene editing via various other methods Citation. The cows are being used because they lack blood donors who can provide plasma to critically wounded patients. Also, the farmer isn’t allowed to use the cows’ blood to produce any products. This is accomplished by replacing the human plasma gene with the one that the cow uses. Scientists remove the ABO gene responsible for plasma generation from the human body, and place it in a cow cell. Next, the cow embryo is electrocuted. This process is very similar to cloning with added gene editing and transgenesis. Depending on which gene is transfected and what donor cell is used (e.g. bone marrow or blood cells), there will be a 5% success rate. However, if the procedure is successful, the individual may not be able reproduce the genes. It is possible to pass those genes on to your offspring if it succeeds. This is because the person possesses those genes from birth, or from the original cell from which it was created. Because humans are becoming more numerous, we use this technology to save our species.
This could have a biological consequence. It is possible that these gene-edited cows will out-breed normal cows one day. Another reason is that we don’t breed donor gene cows with non-disease-prone cows. We have been breeding donor cows for many years. Because not much research has been done on the long-term effects of changing plasma from these cows, it could affect other species such as bacteria or blood sucking parasites, which can impact how other species interact and survive.
To survive over time, a species must have high levels of genetic diversity and variation in their gene pool. If they don’t, all will fail to adapt to new circumstances or to survive new pathogens. This is why, despite all the benefits of gene editing and selective breeding cows, the cows may be affected and the entire species could be at risk. The only way to save a species like the cow created by selective breeding is to kill it. But transgenesis means that the original animal can continue to exist until the gene-edited one replaces it. Genetic editing can make a species so special that it is impossible to breed with them. This could lead directly to the species’ extinction, or close to it.