How much of us can we change through gene therapy ?

[Maciamo]

Following the discussion about how gene therapy and genetic engineering will change future society, I would like to review the potential that either of them have to modify health risks, intelligence, personality as well as physical or psychological traits.

Altering our genes provides an enormous potential for personal enhancement, life extension and cosmetic modifications. But we are not entirely the products of our genes. The environment also plays a big part in modelling who we are. With this in mind, let's see how much we can expect from gene therapy to enhance our lives, or from genetic engineering to design future generations.


Purely genetic factors

Genetic disorders

Fixing genetic disorders, especially single gene diseases like cystic fibrosis or Huntington's disease is the original aim of gene therapy. These conditions can in theory be completely cured by gene therapy.

Phenotype

Someone's physical appearance (known to geneticists as 'phenotype') is almost 100% determined by genes, as demonstrated by the case of identical twins, who look, well, pretty much identical, apart from subtle nuances. However the genetics of morphology is extremely complex, since genes only code for proteins and give very basic building instructions.

Altering one's eye or skin pigmentation is relatively straight-forward, but when it comes to to modify facial features or even body height or structure, it will probably takes several decades before we understand all the underlying genetic mechanisms and even longer before we can effectively determine how to redesign a person's traits. Even when that becomes possible for designer babies, there will still be obstacles in altering the morphology and facial traits of adults.

Muscle mass, body fat, metabolism, skin tone and the like could be changed, but it is doubtful that grown-up bones can still change size and shape simply by modifying their DNA. The genes only provide the recipe for building a body. One's it has been built, changing the recipe won't alter it. Even if genes could be tricked in being reactivated to restart the building process (e.g. using stem cells), there is no guarantee that this will be safe or pain-free.


Mixed genetic and environmental factors

Diseases

A lot of diseases like cancer or cardiovascular diseases are not caused solely by genes, but depend on many environmental factors such as nutrition, stress, pollution, sleep deprivation, and so on. Some genes do confer a protective effect against some conditions, while others can moderately or greatly increased the risks of developing some diseases. Often these genes only affect disease risks indirectly, for example by increasing cholesterol levels or blood sugar levels.

The reason why some people have riskier versions of those genes is that human diets have evolved tremendously over the past 10,000 years, and genes that may have been beneficial with a hunter-gatherer's diet (much less caloric) and nomadic lifestyle (involving a lot of walking) in a cold environment (requiring to burn a lot of calories to keep warm), would become deleterious in people with a sedentary lifestyle with high-caloric intake. Therefore it could be argued that humans ought to adapt their genes to their modern lifestyle, rather than wait tens of thousands of years for evolution and natural selection to do the job. In fact, natural selection wouldn't do the job anymore as virtually all humans live long enough to reproduce before succumbing to genetic maladaptations nowadays.

Intelligence

Intelligence can mean different things to different people. Looking only at IQ scores, the consensus in scientific research, notably identical twin studies, is that between 25% and 75%, or in average 50% is attributable to DNA. The rest depends on environmental factors such as nutrition, education, motivation, opportunities, etc. This means that altering our genes to increase our IQ would only partially work.

Someone with an IQ of 150 is 50 points higher than the population average (which by definition is 100, and is recalculated every year). It could be that that person really possess exceptional genes and grew up in a terrible environment, in which case the genetic factors could be considered to represent most of the 50 extra IQ points. But conversely someone who grew up in an exceptionally nurturing and intellectually stimulating environment, with an ideal nutrition for brain development, could essentially have developed an IQ of 150 through environmental factors with very average genes for intelligence. Besides, there are many types of IQ tests (verbal, visuospatial, logic, problem-solving), and IQ only represent one fraction of our overall intellectual capabilities.

That is why it is so difficult to know at present what genes are truly associated with increased intelligence. Without knowing it, there is no way of enhancing the genes. Even if we could identify the right genes, since the childhood environment is so important in the brain formation, would it really have an effect on adult brains already filled with synaptic connections ?

If genes for intelligence increase the number of neurons or the brain structure during the embryonic development, then gene therapy on adults and even on children wouldn't have any effect. There may also be genes that modify the way neurotransmitters work, or help strengthen synaptic connections more quickly. Such genes could enhance mental faculties in adults, but would probably be more limited to having a better memory and thinking faster, rather than having great capacities at solving problems or having a musical aptitude.

Additionally, genes linked with better cognitive abilities can also cause negative psychological traits, such as higher anxiety, depression or schizophrenia. It would be inconsiderate to decide to get gene therapy to increase one's intelligence by getting as many genes as possible linked with higher intelligence. Working all together those genes may overshoot and cause crippling mental disabilities instead of a well-balanced intelligent person.


Mostly environmental factors

Personality

Even identical twins, with identical genomes, develop different personalities. They may share a similar temperament or similar political orientation or religiosity, all traits that have a moderately high genetic predisposition. But when it comes to personality traits, it has been estimated that only about 20 to 40% depended on DNA.

[Sile]

I like to know if any major illness can alter one's genetic makeup ............do some or any markers mutate due to a severe illness?

[LeBrok]

Fixing genetic disorders, especially single gene diseases like cystic fibrosis or Huntington's disease is the original aim of gene therapy. These conditions can in theory be completely cured by gene therapy.

Obviously the single gene diseases are easiest to fix and will be addressed first.

Phenotype

Someone's physical appearance (known to geneticists as 'phenotype') is almost 100% determined by genes, as demonstrated by the case of identical twins, who look, well, pretty much identical, apart from subtle nuances. However the genetics of morphology is extremely complex, since genes only code for proteins and give very basic building instructions.

Altering one's eye or skin pigmentation is relatively straight-forward, but when it comes to to modify facial features or even body height or structure, it will probably takes several decades before we understand all the underlying genetic mechanisms and even longer before we can effectively determine how to redesign a person's traits. Even when that becomes possible for designer babies, there will still be obstacles in altering the morphology and facial traits of adults.

This will be popular much later when building "designer" babies in 50-100 years.

Muscle mass, body fat, metabolism, skin tone

and the like could be changed, but it is doubtful that grown-up bones can still change size and shape simply by modifying their DNA. The genes only provide the recipe for building a body. One's it has been built, changing the recipe won't alter it. Even if genes could be tricked in being reactivated to restart the building process (e.g. using stem cells), there is no guarantee that this will be safe or pain-free.

Bones and muscles are being renewed and rebuilt all the time. It is not difficult to introduce "bigger muscle and bone" DNA segments to all cells, or just desired cells. Genetically modified viruses (won't make people sick) can be made to penetrate only one type of cell and delivered the fix.

Intelligence

Someone with an IQ of 150 is 50 points higher than the population average (which by definition is 100, and is recalculated every year). It could be that that person really possess exceptional genes and grew up in a terrible environment, in which case the genetic factors could be considered to represent most of the 50 extra IQ points. But conversely someone who grew up in an exceptionally nurturing and intellectually stimulating environment, with an ideal nutrition for brain development, could essentially have developed an IQ of 150 through environmental factors with very average genes for intelligence.

It was more profound in the past when compared intelligence of educated and well fed lords to malnutritioned and uneducated peasants. Today in developed countries everybody is well fed, educated and plays computer games (brain stimulation) from almost a birth. Meaning that almost everyone nowadays can get to 100% IQ capacity.

If genes for intelligence increase the number of neurons or the brain structure during the embryonic development, then gene therapy on adults and even on children wouldn't have any effect. There may also be genes that modify the way neurotransmitters work, or help strengthen synaptic connections more quickly. Such genes could enhance mental faculties in adults, but would probably be more limited to having a better memory and thinking faster, rather than having great capacities at solving problems or having a musical aptitude.

Intelligence need to be addressed at conception. Otherwise the main structure, architecture, the neuronal main connections etc are set by genetic code. It is very doubtful that brain could be rewired by genetic therapy, or rewired to change only intelligence and not personality. However speed of brain might be increased by manipulating chemical balance of brain cells. This will help intelligence if someone has logical brain already. If someone has illogical one it might increase already erratic and stupid behaviour, lol.

Definitely gene therapy can boost memory capacity and memory retention. This is the one I'm waiting for, lol, I will finally remember how to spell correctly and make my writing more accurate.

[Rocketsloth]

Do you think that there's a way this could be addressed in Adulthood ?