Having two arms and two legs, lacking wings and a shell or having a pair of ears symmetrically placed on both sides of the head is due to genes called homeotics, which function as a precise instruction manual. Its mission is to direct the traffic of cells during the construction of our body so that it acquires its three-dimensional shape without errors, both in the external appearance and in the internal structures.
Because modeling an organism in 3D is not easy. When life became complex, you had to create differentiated tissues and make sure they were in the right place.The initial instructions, dictated by the Hox genes, tell the cells if they are part of the head, thorax, abdomen or extremities . Humans emerge from about thirty segments that are formed in an orderly fashion with the precision of a Swiss watch.
Very coiled genes
Researchers from the University of Geneva, Switzerland, revealed that during the first moments of embryonic development, the aforementioned Hox genes are ‘asleep’ and wound like a spool of thread within DNA. At the right moment, the deoxyribonucleic acid chain unwinds and the fragments of genetic material corresponding to the cervical, thoracic, lumbar vertebrae appear on the scene … A new gene emerges from the coil every 90 minutes. All segments of the future person are ready to take the next step and create more complex structures within 48 hours.
The distinction of right and left when locating the organs is also essential, another key step. The neurotransmitter serotonin plays a role in helping the initial ball of cells, the blastula, undergo asymmetric development that puts the liver, pancreas, or heart in place.
In 2017, a study was published that explained in more detail the process by which the heart is located on the left. The genes that induce cell movements remain deactivated after birth. But during embryonic development, cells must move and sometimes travel long distances to get to the right place. For this, certain proteins are necessary, which are the product of the aforementioned genes. These proteins are responsible for converting an immobile cell into a mobile one . If these proteins do not work, the embryo does not progress and dies.
Originally, the heart appears in the midline of the body. But certain asymmetric cellular forces, more prominent from the right, drive the laterality of the heart in vertebrates to the left.
