Inheritance "Like mother, like daughter" – "Like father, like son", says the vernacular. And indeed, children resemble their parents in many ways. Above all physical characteristics are inherited. The blueprint of life lies in the genes. Parents put these in their children's cradles. But what about 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 such as Aristotle noticed that children often resemble their parents in appearance. But at that time, people were still far from understanding how such hereditary traits 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 basic mechanisms of heredity. He crossed pea plants and observed that physical traits are inherited by daughter plants according to specific rules.
Mendel discovered the laws of heredity with pea plants
But it wasn't until the end of the 19. At the beginning of the twentieth century, it became clear that this phenomenon was due to the fusion of female and male germ cells. So-called chromosomes were then later identified as the carriers of hereditary information.
Today it is known that in human reproduction 23 chromosomes are passed from each parent to the child. In every cell of the body there is thus a duplicate version of the blueprint of life.
What we become is determined by our genes. About 25.000 genes are located on the chromosomes. It is they who are responsible for our appearance, and they also control all the metabolic processes in our body.
Genes and hereditary diseases
Once the structure of our genetic makeup had been elucidated, the search for specific genes began. Geneticists wanted to know more about function. Knowing the tasks of the individual genes.
It has been known for some time that the cause of many diseases can also lie in the genetic material. Diabetes, cystic fibrosis, cancer – almost 4000 hereditary diseases are known today, but most of them occur only rarely.
Since each gene is present in duplicate, not every genetic defect must immediately lead to the outbreak of the disease. It is also possible that the predisposition for the disease is simply inherited from one parent.
A child receives 23 chromosomes from each 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.
Today, a woman can have her individual risk of breast cancer determined by a genetic test. Modern genetics makes it possible. The 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, the knowledge of the risk alone can completely change the everyday life of an affected person. It is also possible that women with a family history would be better advised to have the usual preventive examinations at regular intervals.
The genetic makeup under the magnifying glass
Insight into the genome holds many opportunities, but also risks. Genetic tests can reveal a risk of disease at an early stage. To enable rapid medical care.
On the other hand, it might also be tempting to intervene therapeutically or manipulatively in the genetic material. Today's genetic engineering possibilities are the subject of intense social debate. Demand clear – preferably transnational – legal regulations.
So-called prenatal diagnostics are standard today. Amniocentesis or blood tests can be used to screen embryos at an early stage for genetic diseases such as trisomy 21. Especially older couples are recommended to undergo such an examination, because the risk of inherited "chromosomal anomalies" is higher increases sharply at the age of more than 40 years.
Nowadays, however, possible genetic defects could be tested much earlier. For example, in the case of artificial insemination in a test tube, before the fertilized egg of the future mother is implanted.
Advocates of this so-called pre-implantation diagnostics, which the Federal Court of Justice allowed in 2010, argue: In this way, it can be ensured that only healthy embryos are implanted.
But with this method, it would also be possible to test the fertilized egg cell for desired genetic characteristics. For example, to determine the color of the hair or eyes, or the "sex as desired" is conceivable and feasible.
But who makes the decision about which embryo to implant and which not?? This clearly shows how fine the line is between what is technically feasible on the one hand and morals and ethics on the other.
Artificial insemination often already involves "selection instead of
The power and powerlessness of genes
The role and function of many genes in body structure and metabolism are now known. And research continues to make rapid progress. But what do genes have to do with the development of our personality??
Are character traits also inherited, or do genes only play a rather subordinate role in this context?? What is inherited, what is learned over the course of a lifetime? These questions have been the subject of controversial debate in research for decades.
Meanwhile, there is evidence that genes also offer a kind of blueprint for personality. However, this only determines the framework conditions: How the personality develops within these framework conditions depends strongly on environmental factors such as upbringing, education, social environment or experiences.
Thus, temperament, fearfulness or aggressiveness seem to be inherited to a certain extent. However, the expression is strongly influenced by the environment. Traits that are related to culture, such as musicality or religiosity, are more likely to be modulated by environmental factors.
What twin research reveals
Identical twins have identical genetic makeup. In this respect they are ideal "test objects", to investigate environmental influences on the expression of the genetic makeup. For example, personality traits of identical twins who grew up separately were studied.
In other words, those who have been exposed to various environmental factors. Very often identical twins nevertheless develop very similar personality structures. Preferences – an indication of the existence of genetic components in personality development.
Findings in pathological personality changes, for example in schizophrenia, have also been interesting. If one twin falls ill, the other twin has a 50 percent risk of also contracting the disease. So both genetic makeup and environmental factors seem to play a role.