Genetic engineering, also called genetic modification and going by a number of other loose identifiers as well, is the purposeful manipulation of deoxyribonucleic acid (DNA) to alter an organism's genes using laboratory techniques.

It involves gene cloning, or the reproduction of a multitude of copies of a specific sequence of DNA that holds the genetic code for a specific protein product.

Once the genetic material of interest has been isolated from its parent DNA, it must be introduced into a strand of existing DNA from a different source for it to exert its function.

This strand of "mixed" DNA is called recombinant DNA. In essence, the "grafted" DNA makes used of the cellular machinery of the environment into which it has been introduced, and the cloned gene is expressed (that is, the protein it codes for is synthesized) in the hybrid strand of DNA.

The advent of molecular cell biology soon gave way to the undertaking and completion of the Human Genome Project. Since just the start of the "new millennium," humankind's understanding of applied genetics, and the tools at the disposal of researchers worldwide, have blossomed dramatically.

But with increased possibilities in areas such as cloning come increased responsibilities, given what is at stake for future generations. What are the ethical issues with this technology, and what is the state of ethics in genetic engineering as a discipline?

An example of genetic alteration as applied to microbes gives a good overview of the general DNA engineering process.

First, if you are in charge of such a project, your engineering team needs to find a gene worth amplifying – in other words, replicating – or incorporating into a new organism.

For example, what if you could give certain frogs the ability to glow in the dark? For this, you would need to first identify another organism possessing this trait and then determine the precise DNA sequence, or gene, that confers for this ability, such as by coding for a photoluminescent protein.

You then need to decide where in the target DNA (i.e., that of the frog) the gene will go. You also have to find a vector to get the gene to the target. A vector is a piece of DNA into which the gene can be inserted for transfer into the recipient organism. Often, this vector comes from bacteria or yeast.

You'll also need to find an appropriate restriction endonucleases, which are enzymes that cut out short (four to eight bases) segments of DNA so that other lengths of DNA can be inserted in their place. Finally, the target and vector DNA are blended in the presence of DNA ligase, an enzyme that links them together to produce recombinant DNA.

On the whole, the process is very simple, at least from a theoretical standpoint.

Genetic engineering is any process in which a gene is manipulated, changed, deleted or adjusted so as to amplify, change or adjust a certain characteristic of an organism. In other words, it encompasses a very broad range of unique chemical alterations, given the number of traits available for manipulation in eukaryotic organisms (animals, plants and fungi).

The counterparts of eukaryotes in the living world, the prokaryotes, are almost all single-celled and have a comparatively tiny amount of DNA. As you might expect, it is much easier from a technical standpoint to manipulate the genome (the sum of all DNA in an organism's chromosomes) of a bacteria than it is that of, say, a goat.

But at the same time, genetic engineering research on bacteria, in addition to being all that was really feasible in the early days of genetic modification, also avoided virtually all ethical issues because no one was concerned for the welfare of bacteria.

But the rapid approach of the day when it will be possible to replicate entire human beings is spurring all manner of fresh ethical debates in the scientific community and beyond.

While genetic engineering has uses that are, on balance, beneficial to society, certain applications can raise ethical concerns, especially with animal and human rights.

For example, while the lighthearted example of a glow-in-the-dark frog was meant in jest, it is true that actually creating such an animal would be fraught with ethical issues. For example, why make an animal more susceptible to nocturnal predators by making it easier to see?

By the end of the first decade of the 21st century, bioethicists, sociologists, anthropologists and other observers were already weighing in on issues that had yet to fully rear their heads owing to practical or technological barriers that were expected to fall by the wayside as genetic engineering became more advanced and refined.

Many of these were fairly easy to imagine (e.g., the cloning of humans); others were far more subtle. Few, of course, have easy or definite answers.

Some of the repercussions of being able to test for, much less mimic, certain genes are not easily confronted. For example, if medical science allowed you to determine if a child you just conceived and is now in your or your partner's womb is carrying the gene for a fatal disease, how might you react?

Would it change anything of the disease had an onset later in life? Would you feel an ethical responsibility to tell the child during his or her life if the pregnancy resulted in the live birth of an apparently healthy baby?

People are often inclined to talk about genetic engineering as if it were a future-only concept. But in fact, it is already here and deeply entrenched in a number of everyday applications. As a result, ethical conundrums are already upon the world.

Agricultural: One need not be a high-end news junkie to be aware of the ongoing controversy involving genetically modified foods. often called GMOs (for "genetically modified organisms"). A full treatment of this topic alone would require several articles at least as long as this one.

Artificial selection (breeding): The genetic manipulation of animal reproduction throughout modern human history has not traditionally required focused microbiological techniques. However, selective breeding between dogs whose DNA complement for certain traits has been mapped for many generations is a form of organism-level genetic engineering.

Gene therapy: Genetic engineering allows for the delivery of working genes to patients whose own DNA does not include these genes. See the Resources for an article on a study making use of this technique in Parkinson’s disease, a neurodegenerative disorder that affects about a half a million Americans.

Cloning: This generally refers to making an exact copy of a DNA strand, but it can also be used to clone (that is, duplicate) an entire organism.

Pharmaceutical industry: Genetic modification can be used to create prokaryotic micro-organisms that can make chemicals (e.g., proteins or hormones) to make medicines or treatments for human benefit. This takes advantage of the very short generation times (that is, the rate of reproduction) of most bacteria.

Perhaps the most looming issue in the realm of genetic engineering, surpassing even GMO foods, is the emergence of CRISPR, which stands for clustered regularly interspaced short palindromic repeats.

These short DNA sequences from bacteria can be used to create corresponding RNA sequences and, with the help of an enzyme called Cas9, can be employed to "sneak" DNA sequences into the human genome or remove others. Hence the term "gene editing" is often seen in the context of discussions of CRISPR.

The real implication of CRISPR is that the procedure can be used not only to adjust and manipulate the genes of humans per se, but of human embryos, allowing for the possibility of "designer babies." This could result in the "manufacture" of only certain types of people (e.g., those with a specific eye color, ethnic profile, intelligence level, overall looks and strength, and so on). While everyone wants strong, healthy babies, is using biotechnology to get there ethical?

Also, as with any new technology, it is not possible to know the long-term impact of changing someone's (or any organism's) DNA in this manner.

Thus, in addition to concerns about "playing God" and overstepping the bounds some people feel nature has naturally put in place, there are practical health concerns: Genetically engineered organisms made using discoveries like CRISPR look great when they're brand new, but how will they stand basic tests of time?

Agricultural impact: The genetic modification of of certain plants (and the patents for those plants) means that farmers not using those seeds are more likely go out of business. Also, if their seeds are even accidentally crossed with patented seeds, they can be sued, even if it was simply because of the environment or unavoidable cross-pollination.

Many of these plants are resistant to the herbicides used to kill weeds and competing plants, but some these herbicides are also toxic to humans, introducing another ethical issue.

GMO plants can also impact the natural ecosystem by transferring these new genes to other plants; the long-term impact on the environment cannot yet be known.

Animal rights: Certain forms of genetic engineering appear on their face to be animal-rights violations. Livestock animals such as chickens are often engineered to grow larger breasts, which makes existing and living painful and almost impossible. These types of modifications make the meat better for human consumers, but unquestionably adds difficulty and pain to the lives of animals.

It is hard to square this with "ethical" behavior in the mind of anyone who assigns importance to the idea of sentient creatures undergoing unnecessary suffering.

Earlier, breeding was mentioned as a form of genetic engineering. Dog breeding is one area in which the hazards of this practice have been well-publicized, though dog breeding nevertheless remains popular. Breeders often attempt to use genetically limited specimens to make "purebred" lines (and again, artificial selection is a form of genetic engineering, drawing on the same evolutionary principles that natural selection does).

These animals are often riddled with health problems, largely because of the preservation of harmful genes that would have naturally fallen out of the population but persist because of dog breeding.

Eliminating “bad" genes: The basic allure of genetic engineering for many people is not that it could create something super, but that it could eliminate something that is already here but unwanted. CRISPR and related technologies could lead to the ability to delete harmful genes or, more chillingly, get rid of people or organisms with genes that lead to chronic diseases or that lead to mental illnesses.

Is this ethical? What if these superficially “bad” genes actually serve a good purpose, like the “sickle cell" gene does in its heterozygous form, often offering protection against malaria? It is not wrong to want to “get rid of” mental illness, but the idea of eliminating people who might develop mental illness later but are free of it today should chill the blood of any citizen.

And even if it might be known for certain that some people would develop terrible mental illness, does that mean that such people, who never asked for any of their DNA and have no hand in causing problems in their own genomes, should be denied a chance at life? Who are the ethicists representing those consigned by accidents of birth to very troubled lives?

Changes in genetic diversity: Eliminating "bad genes" and selecting only for "good traits" could result in plants, animals and people being too genetically similar. This makes humans and other organisms more vulnerable to diseases and the risk of sickness taking out larger swaths of the population. It also interferes with natural selection, evolutionary processes and population genetics, all of which, however slowly and sometimes clumsily, tend to do an adequate job of keeping the biosphere in order.