Do we share 60% of our DNA with bananas? This statement circulates a lot as a scientific curiosity, but it is absolutely false And the result of an incorrect interpretation of a genetic study (never published) that dates back to 2013. By taking the trouble to view the study and what have actually said its authors, the reality is very different: our genome has in common the 60% of gene with that of the banana plant, which corresponds to about the1% of the overall DNA of the two species. In addition, proteins codified by this 60% of genes in common, only the 40% They are identical in the sequence of amino acids that make them up.
How much DNA we share with the banana: where the myth of 60% is born
The idea that humans and bananas share a high percentage of DNA probably originates from a project of National Human Genome Research Institute American, conducted in 2013. The results of this research, led by the geneticist Lawrence Brodythey were never published in a scientific magazine, but were used for an educational video of the Smithsonian Museum of Natural History.
The DNA It is the custodian of the genetic information of each organism, a unique sequence of four “letters” (the nitrogen bases: adenine, cytosine, cheek And fear) which makes us distinct not only from other species, but also between individuals of the same species. The human genome is imposing, composed of about 3 billion of nitrogen base couples, of which a small part (about the 2%) is organized in gene that contain the Instructions to produce proteins.
Specifically, DNA is divided into two categories:
- Coding DNA: constitutes about the 2% of our genome and is composed of gene. These genes contain the instructions for the synthesis of proteins that perform almost all cellular functions and determine our characteristics.
- DNA non -coding: includes the rest 98% DNA. It was once mistakenly labeled as “garbage DNA” (or “Junk DNA“) Because it was believed to have no function. However, scientific research has gradually revealed that much of this DNA performs crucial roles in regulating gene expression (checking when and where the genes are activated or deactivated), the protection of the ends of the chromosomes and the modulation of the DNA structure.
Brody’s study has identified, in over 4 million comparisons between the genes of the two species, approximately 7000 correspondences between the genes of banan and human ones. This is equivalent to saying that a part of our genes has one recognizable counterparty in the banana genome. It is important, however, to underline that these correspondences do not indicate perfect complementarity. As the geneticist explained, the proteins codified by these homologous genes (i.e. that perform the same function for different species) are identical in 40% of cases.
Consequently, the statistics must be interpreted precisely: instead of a 60% similarity of our total DNA with a banana, the reality is that the 60% of 2% of our DNA (the coding one for proteins), i.e. the1% about the total of our genome, produces proteins which are identical in a 40% correspondences.
Human beings, bananas and other species have genes in common because we have a single common ancestor
The sharing of a part of our genetic heritage with apparently distant organisms such as bananas, chimpanzees or mice is not surprising at all and this is precisely the study field of comparative genomic.
But why We share part of our genetic heritage Even with apparently very distant species, how in this case the banana plant? The reason is simple: all living organisms on Earth descend from a only common ancestor. About 4 billion years ago, a single cellular population, known as LUCA (Last Universal Common Ancestor“Last universal common ancestor”), gave rise to the only evolutionary line which then branched off in the entire “tree of life” that populates the planet Earth. This common descendant means that the Basic cellular functions have been preserved through evolution. Whether it is an animal or vegetable cell, vital processes such as the breathing of oxygen and the metabolic reactions Essential for survival are carried out by very similar transversal mechanisms for all living species.
It may be surprised to know that the human being has about 25,000 genesas emerged from the human genome project, while a banan tree has about 36,000. This clearly shows that the complexity of an organism is not directly proportional to the number of genes it has. However, many of the genes present both in humans and bananas, despite our obvious differences, are homologous genesthat is, they share a common origin and perform the same function in different species.
The presence of these geniuses in such different species underlines the interconnection of life on earth and the efficiency with which nature reuse and adapt the fundamental genetic solutions.
