a bit of science

DNA is the building block of life, and it is a blueprint which gives instructions for how the body should function. DNA structure is specific to every species and each of them has its own unique DNA. DNA, or deoxyribonucleic acid, is a polymer composed of nucleotides. Nucleotides are composed of three key components, a sugar group, a phosphate group, and for four bases (Adenine, Thymine, Guanine, and Cytosine). The A, T, G and C bases form specific sequences called genes. Genes contain guidelines for creating various proteins. The human DNA has 22 pairs of chromosomes and one additional pair of chromosomes (the 23rd) which determines the sex of the individual (X and Y chromosomes). For each pair of chromosomes, one is inherited from the mother and the other from the father. Even though the species have the same DNA structure, what differentiates the individual are the DNA variants (specific for every human being).

The researchers have found a certain pattern of geographical distribution of genes, specifically scientists observe different frequencies of DNA variants in distinct regions around the world (people were sedentary for large periods of time throughout the global history). The startup company “23 & Me” offers various services of DNA analysis, but their key product is the Ancestry and Traits composition test. They have invented an algorithm which combines information about the distinct variants patterns “with the unique set of DNA alleles in your genome to estimate your genetic ancestry. 22 chromosome pairs and the X chromosome pair are analyzed to determine the ancestry composition of a person” (“23&Me” webpage – https://www.23andme.com).

The ancestry reports also determine maternal haplogroups and neanderthal DNA (yes, you read it correctly, neanderthal DNA). To determine maternal haplogroups, “23& Me” explores genetic variants in our mitochondrial DNA. The mitochondria is an organelle inside the cell which has a function of turning food into energy. The mitochondria is actually a bacterial cell which billions of years ago was engulfed by another cell. Instead of becoming breakfast it merged with its predator, becoming an integral part of a larger cell. Mitochondrial DNA is the DNA contained inside the mitochondria and it is only passed down from mother to daughter, helping the tracing the maternal lines throughout history. Over generations, genetic variants occur in the structure of the mitochondrial DNA, creating different maternal lines around the world. Thus, facilitating the tracking of the human migrations throughout time and place.

Coming back to my previous mention of the neanderthal DNA. For decades the prevailing scientific consensus was that the poor Neanderthals were exterminated in the history’s first genocide perpetrated by the Homo Sapiens. We are quite a violent bunch of bullies, aren’t we? However, in 2010 scientists decoded the neanderthal genome in our own DNA. These findings do not contradict the previous ones, but they prove that our ancestors fooled around with the Neanderthals, maybe even fully integrating these subspecies into our own genetic mix. Since then, further studies have been done claiming that not only did we mix with the Neanderthals, but also with Denisovans whose DNA can be tracked in the people with Asian or Oceanic background. According to the “23 & Me” webpage “you can have a genetic variant that evolved in Neanderthals and came back into the human lineage when the two groups interbred. Because you inherit variants from both of your parents, you can have 0, 1, or 2 copies of the Neanderthal variant at each marker”.