Since the discovery of the code of life scientists have looked at ways to tinker with it to change some of life characteristics. Over the last 10 years (CRISPR was discovered in 1993 and Cas9 in 2005 but their application to the splicing of DNA can be dated to 2013) researchers have been able to modify DNA strands removing and inserting snippets of DNA taken from genes of different species. The trick is easy to understand (although it is no so easy to carry out): a gene has been discovered to be the code for a certain protein production in a given species. Using CRISPR/Cas9 it is possible to separate those instructions (that strand of codons) from a gene and then, again using CRISPR/Cas9 to splice them into a gene of the target species. When that gene will be activated it will lead to the coding of the desired protein.
In this way it has been possible to add some (desirable) characteristics to a bacteria by borrowing them from a different species. Codons, i.e. the coding of proteins, are exactly the same in all species, hence it is possible to transplant them from one species to a different one without any “rejection” from the target species.
However, the protein resulting from those instructions may not be accepted by the organisms, or it may lead to side effect. The key issue is that the characteristics of a living being, its phenotype, depends on the genetic code (the genotype) but there is no one-to-one correspondence between a gene (and its DNA strand) and a single characteristic. A variation in a gene may lead to the living organism displaying a desired characteristic but at the same time it might create undesired characteristics that may become apparent only at a later stage.
Significant effort is under way to understand what would be the overall impact of a gene modification on the phenotype of that organisms. The use of artificial intelligence (deep learning) made possible by the huge quantity of data that are being harvested from the modification of genes promises to deliver a tool for connecting the genotype with the phenotype. This might become available in the next decade.
In perspective, it should become possible to design the changes of a gene to obtain the desired change in the phenotype, probably in the 2040-2050 timeframe. Notice that not all potentially desired changes will become possible. As an example the number of fingers in mammals is governed by specific genes (Hox genes). Altering of those genes may result in extra fingers but it carries along non-favorable characteristics, hence the reason why mammals did not diversify the number of fingers (fingers can be fused together like in horses, but they are still 5, genetically speaking…). By altering those genes to get an extra thumb you are also creating side effects that hamper the reproduction chances of that modified individual, thus leading to an extinction of those genetic characteristics.
Another crucial issue is that once a gene has been modified that modification will be passed on (if it is encoded in a reproductive cell) to the offsprings with the potential of generating undesired effects that are difficult to foresee.By 2020 researchers expect to have a tool similar to CRISPR/Cas9 that can be used to change the RNA. This would still allow the creation of desired protein but the mutation will not be passed on to offsprings (traits inheritance occurs only via DNA).
It is also become possible to use viruses, billions of them, as vector to change the DNA of cells in a grown up individual and some companies, like Sangamo, are experimenting in this area; a first human trial took place in 2017.So far the focus of researchers has been on curing genetic disorders/diseases but it is clear that there is a potential for human augmentation (carrying along many ethical issues).
Notice that we are still very far from the point of having the knowledge required to “augment” a human being. One thing is to modify a gene to restore the normal “coding”, a completely different case is to create a code to achieve a certain result, particularly in certain areas. As an example we have very little (close to zero) understanding of what makes intelligence emerging in a brain, hence it is impossible today to imagine a modification of the genome to augment intelligence.
Extending human life, on the other hand, by extending the telomeres seem within the domain of (future) feasibility since several studies have identified in the shortening of telomeres a reason for ageing. This would be a sort of human augmentation.