The DNA determines our personality

Inheritance

The blueprint of life

The blueprint of life is in the genes and parents put their children in the cradle with them. But what about the personality? Are character traits also inherited or does the environment play a decisive role in our development? What is inherited, what is learned?

Even in antiquity, philosophers like Aristotle noticed that children often outwardly resemble their parents. But at that time we were still far from understanding how such genes are passed on to offspring. It took many centuries until the phenomenon was discovered.

It was not until 1865 that the Augustinian monk Gregor Johann Mendel discovered the first fundamental mechanisms of inheritance. He crossed pea plants and observed that physical traits are passed on to daughter plants according to certain rules.

But it was not until the end of the 19th century that it became clear that this phenomenon is based on the fusion of female and male germ cells. So-called chromosomes were later identified as the carriers of the genetic information.

And in 1953, James Watson and Francis Crick finally managed to break down the structure of the DNA that makes up a chromosome. The chromosome is made up of a long DNA thread that is finely twisted in the form of a double helix in the cell nucleus.

Today we know that in human reproduction, 23 chromosomes are passed on from each parent to the child. In every cell of the body there is thus a double execution of the blueprint for life.

Genes determine what becomes of us. There are around 25,000 genes on chromosomes. It is they who are responsible for our appearance and they also control all metabolic processes in our body.

Genes and Hereditary Diseases

After the structure of our genome had been clarified, a targeted search for genes began. The geneticists wanted to know more about the function and tasks of the individual genes.

It has long been known that the cause of many diseases can also lie in the genetic make-up. Diabetes, cystic fibrosis, cancer - almost 4,000 hereditary diseases are known today, but most of them rarely occur.

Since every gene is available in duplicate, not every gene defect has to lead to the onset of the disease immediately. The predisposition for the disease can also simply be inherited from one parent.

The best example of such a predisposition is familial breast cancer. If many women in the family have already had breast cancer, there is an increased likelihood that a defective gene has been inherited.

A woman can now have the individual breast cancer risk determined using a genetic test. Modern genetics make it possible. The only question is: how useful is such a test? Even if there is a predisposition to breast cancer, the disease does not necessarily have to break out.

However, just knowing about the risk can completely change the everyday life of an affected person. It is possible that women with a family history would be better advised to have the usual preventive examinations carried out at regular intervals.

The genetic material under the microscope

The insight into the genome harbors many opportunities, but also risks. Genetic tests can reveal the risk of disease at an early stage and thus enable rapid medical care.

On the other hand, it might also be tempting to intervene therapeutically or manipulatively in the genome. Today's genetic engineering options are intensely discussed in society and require clear - ideally transnational - legal regulations.

The so-called prenatal diagnosis is standard today. Early embryos can be examined for genetic diseases such as trisomy 21 (mongolism) via amniotic fluid examinations or blood tests. Such an examination is particularly recommended for older couples because the risk of inherited "chromosomal abnormalities" increases sharply after the age of 40.

However, possible genetic defects could also be tested much earlier nowadays. For example, in the case of artificial insemination in a test tube, even before the fertilized egg cell is implanted in the coming mother.

Proponents of this so-called pre-implantation diagnosis, which the German Federal Court of Justice allowed in 2010, argue: In this way one can ensure that only healthy embryos are implanted.

But with this method it would also be possible to test the fertilized egg cell for desired genetic properties. For example, to determine hair or eye color, and the "gender as desired" is conceivable and feasible.

But who makes the decision about which embryo is implanted and which not? Here it becomes clear how thin the line is between what is technically feasible on the one hand and morality and ethics on the other.

About the power and powerlessness of genes

The role and function of many genes in body structure and metabolism are now known. And research is rapidly making great strides. But what do genes have to do with the development of our personality?

Are character traits also inherited, or do genes only play a subordinate role in this context? What is inherited, what is learned in the course of life? These questions have been discussed controversially in research for decades.

There is now evidence that genes also offer a kind of blueprint for personality. However, this only defines the framework conditions: How the personality develops within these framework conditions depends heavily on environmental factors such as upbringing, training, social environment or experience.

Temperament, fearfulness or aggressiveness seem to be put in our cradle to a certain extent. The expression, however, is strongly influenced by the environment. Properties that can be seen in connection with culture, such as musicality or religiosity, are more likely to be modulated by environmental factors.

What twin research reveals

Identical twins have an identical genetic makeup. In this respect, they are ideal "test objects" to investigate environmental influences on the expression of the genetic make-up. For example, the personality traits of identical twins who grew up separately from one another were examined.

In other words: the various environmental factors were exposed. Very often identical twins nevertheless develop very similar personality structures and preferences - an indication of the existence of genetic components in personality development.

Findings in pathological personality changes, for example in schizophrenia, were also of interest. If one twin falls ill, the other twin has a 50 percent risk of contracting it as well. Both genetic makeup and environmental factors seem to play a role.