People have always been curious to know why children are similar to parents and grandparents. They have also wondered why a plant that produces small fruits, originates another plant with similar fruits. These questions marked the beginning of knowledge about inheritance and later about genetics, science that was born as a branch of biology, from the first plant crossing experiments carried out by the Augustinian monk Gregor Mendel.
Historical background to Mendel's work.
All the explanations about the mechanisms of the biological inheritance made before Mendel resulted in approximations to the truth, without going beyond being suppositions, since they lacked scientific rigor. However, the previous works kept alive the curiosity to know the mechanisms of the inheritance, and that restlessness led to the elaboration of the true principles of the biological inheritance. Among the theories about the mechanisms of inheritance that came from Mendel's work, we can mention:
- Preformism.
The first defender of this theory was the Italian physician Giuseppe Degli Aromatari (1586-1660). The preformism postulated that in the ovum or sperm was already present and "formed" the fetus as a small man, called "homunculus." This little man was endowed with the different parts of the body, although as their dimensions were very small or were in a liquid state, they were not completely visible.
A) Yes. As the fetus developed, the gradual solidification of each part occurred, and the organism increased in volume. Among the most famous preformists include the physiologist Albrecht von Haller (1708-1777) and the microscopists Charles Bonnet (1720-1793), François de Plantade (1670-1741), Marcello Malpighi (1628-1694), Jan Swammerdam (1637-1680) ) and Anton van Leeuwenhoek (1632-1723). With the progress and improvement of the microscopes, it was proved that what looked like a little man in the sperm was the structure of the head, known as acrosome, which contains enzymes that facilitate the process of fertilization.