When a group of scientists announced in 2001 that they had sequenced the human genome, actually what they said was a bit of a lie. Well, in honor of the truth, they didn’t lie, because in the study published at the time in Nature they clarified that they had deciphered only one 92% of the same. However, we already know how it works sometimes: that scientific rigor does not ruin a good title for you. It was reported that the entire genome had been sequenced, but only 8% remained a mystery to science. At least until now, because we can finally say with all the letters that this time the human genome has been completely sequenced.
Scientists have done it Telomere-2-Telomer (T2T)a global collaboration to complete the missing sections in the original human genome assembly.
This discovery led to the publication of six studies in Science and twelve others in other media. In each of them, they delve into one way or another the methods used and what it means to be in possession of all the human genome. And it is that deciphering that 8% was not just a thorn in the side for scientists. It is also very useful, because in this mysterious part of our genetic material there are structures of great importance this can provide us with very important data, both in medicine and for the study of our variability and our evolution as a species.
The missing pieces of the human genome puzzle
What scientists from Human Genome Project he was a big step. For the first time, we were in possession of an almost complete map of our genetic material. It has been used since in Medication to search for possible pathogenic mutations. And also in genetics to study the variability of our species.
It was a big step and basically the only thing that could be done with the tools they had at the time. Generally speaking, what was done then was to take the 23 pairs of chromosomes which make up the DNA of a human being and cut this genetic material into very small parts, since it was the only thing sequencing systems of the time could read. In total, the human genome has a little more than 6 billion letters and the fragments that were fabricated had between hundreds and thousands of letters.
These results can be very useful for studying the genetic variability of the human species, as well as pathogenic mutations.
Once these parts were obtained, what was done with the available tools was to read them as they were reassembled in the the right order. The problem is that the human genome contains what is called repeat sequence fragments. That is, long pieces of DNA in which the same letter is repeated all the time. When it comes to dealing with this, something happens like when we put together a puzzle with lots of sky. In this case it’s even worse, because there were exactly the same parts. That’s why that 8% undecrypted largely corresponds to repeated sequences. But fortunately, genetic sequencing tools have evolved a lot over the past 20 years and it is now possible to put all the pieces back together.
The problem of mixing mum and dad’s DNA
Nowadays the new long-read DNA technology it can read longer fragments than could be read in 2001. Returning to the puzzle comparison, if the sky is broken up into very small fragments, it is impossible to know where each is going. But if larger pieces are used, it is possible to find the subtle differences between them that indicate where they should be placed.
But that wasn’t the only challenge they faced during this first major human genome sequencing. And it is not easy to cope with it either. mixing of two genomes: the maternal and the paternal. The combination of the two in an individual’s cells gave rise to certain unknowns when performing sequencing.
Therefore, this time they worked with an unusual cell line. It comes from a non-cancerous tumor called hydatidiform mole, which essentially consists of a human embryo that has discarded maternal DNA and duplicated paternal one. Thus, the problems associated with mixing two genomes are avoided.
Gaps in the human genome revealed
DNA is the instruction book of an organism. It contains all the instructions for it to work properly. But these instructions are in a language cells cannot read.
for them to run DNA must be transcribed into RNA and then translated into protein. This translation is accomplished by following something known as genetic code. It’s a kind of language in which each group of three letters of RNA means the same thing as one of the amino acids that make up proteins. It is important to keep this in mind, as the terms “genetic code” and “human genome” are often incorrectly used interchangeably, even though they are not the same.
The terms “genetic code” and “human genome” should not be confused, as they are not identical.
But going back to proteins, not all DNA ends up being translated to give rise to one. There are fragments that actually have other functions. They are generally known as “junk DNA” even if they are not useless at all. Part of that 8% of the human genome that could not be sequenced contains this unwanted DNA. Although there is also coding DNA.
More specifically, from 19,969 protein-coding genes there are in the human genome, 2,000 have been discovered in this latest batch. Most of them are handicapped, but there are 115 who can still express themselves and translate.
Another interesting fact of this new and exhaustive reading is that they found approximately 2 million more variants in the human genome. Of all, 622 are linked to medically relevant genes.
And, as if all that weren’t enough, it turns out that a good part of these new discoveries are related to two very important structures of chromosomes: telomeres and centromeres.
The former are a kind of cap found at the ends of chromosomes to protect them from DNA degeneration that occurs when they cells divide. This structure is closely related to the agingits study and knowledge are therefore essential.
Regarding the centromeres, it is the central structure of the chromosome by which the two arms of the chromosome come together during DNA duplication. They have an essential role in cell division, to ensure that the genetic material is evenly distributed and, therefore, there are no cells with more or fewer chromosomes than normal.
New clues to the evolution of our species
A thorough understanding of the human genome can also be very helpful in understanding why the human species evolved like he did and got so far away from other primates.
In this hidden 8% there was also interesting information to understand this case. For example, as explained in a press release from one of the members of T2T, Evan Eichler, “the complete genome sequence reveals that some genes associated with larger brains are highly variable.” In fact, “one person may have 10 copies of a particular gene, while others may only have one or two.” This can give us many clues.
In short, what is announced today is an important step. Not just because it shows that science has advanced enough to complete what was abandoned 20 years ago as impossible. Also because this new reading has given us information of great interest on who we are, why we get sick or how we age. These are vital questions for human beings. We now have new information to answer them, although it may take a little digging to find all the answers.
