Finally, we now have a complete picture of the human genome. A new beginning!
The genome contains a wealth of information. Therefore, scientists are trying to discover the genetic code for the animals And the vegetables, but of course also from humans to crack. About twenty years ago we were almost there; Scientists have managed to decode about 92 percent of the human genome. But now researchers are bringing in big news. Because the last eight percent are now set, too.
DNA alphabet
You can think of the genome as a thick book written in the four-letter DNA alphabet: A, T, G, and C. Chromosomes are the seasons and genes are the words. Among the functional genes, you will also find a lot of nonsense as if a cat was walking over a keyboard while writing this book. The goal of genomicists is to put all the words and nonsense in the correct order. In addition, each vertebra must be attached to the correct segregation (chromosome). This does not seem like a difficult task, were it not for the fact that the text – in the case of the human genome – is about 6 billion characters long. start up.
Deciphering the human genome is a hell of a job. That’s because the human genome is made up of just over six billion individual DNA letters, spread over 23 pairs of chromosomes (see box). To be able to read the genome, the scientists first cut all this DNA into fragments of hundreds to thousands of letters. Then the sequencers read the individual letters into each piece. Then the scientists try to put the pieces together in the correct order, like putting together a complex puzzle.
repetition
However, the main challenge is that some parts of the genome repeat the same letters over and over. Repeating regions include centromeres (the parts that hold chromosomes together and play an important role in cell division) and ribosomal DNA (the molecular compounds that drive protein synthesis). Still other recurring parts include new genes that can help the species adapt. In the human genome, we find millions of repetitive DNA sequences of 300 letters, scattered here and there in the genome. In the past, all this repetition made it impossible to put a few pieces together in the correct order. It’s like having identical pieces of a puzzle – scientists didn’t know which one went where, leaving huge gaps in the genome image.
eight percent
However, researchers were able to come a long way in 2001. As mentioned, the original human genome sequence left only eight percent of the DNA. There was a good reason why these eight percent could not be deciphered any more. Scientists knew that these missing fragments contained nearly identical copies and highly repetitive sequences. “These are important areas, but they are difficult to categorize,” researcher Megan Dennis said.
Leap Forward
However, new technologies now make it possible to decipher the last eight percent – which is comparable in size to the entire chromosome. That’s because previous DNA sequencing technology was only able to read relatively short sequences. “Newer generations of sequencers can decode much longer stretches, up to a million base pairs or ‘letters’ of DNA,” Dennis said. “This means that the pieces are much larger and therefore easier to assemble in the original order. This is real game changer†
complete human genome
Researchers have finally got it right. In the new study, they describe the entire human genome; And thus also the tricky parts on which scientists had not previously dared to burn their fingers. The new reference genome comes from a single human sample – but not from a real person. The researchers sequenced the entire genome using a special cell line that contains two identical copies of each chromosome — unlike most human cells, which carry two slightly different copies. Most of the newly added DNA sequences are located near the repetitive telomeres (the long and posterior ends of each chromosome) and the aforementioned mediators (the dense middle sections of each chromosome). “In the genetic manuscript, we see chapters that have never been read before,” said study researcher Evan Eichler. Or, in the words of geneticist Robert Waterston of the University of Washington, “there are no more hidden or unknown parts.”
“The study has major implications for our understanding of human evolution, diversity, and biological function.”
new insights
What is remarkable about the human genome, among other things, is that a large amount of human genetic material consists of long and repetitive sections, which occur over and over again. While every human has some representatives, not everyone has the same number. And the difference in the number of repeats is where most of the human genetic variation is. But this is not the only new insight. It is one of the many important outcomes of the project. “It was worth the wait,” said Francis Collins, an American physician and geneticist. “The study reveals a rich set of surprising architectural features, with major implications for understanding human evolution, diversity, and biological function.”
Overall, the results are a huge milestone. “Since we obtained the first conceptual sequencing of the human genome, it has been difficult to determine the exact order of complex genomic regions,” Eichler says. “I am really glad we got the job done. This whole view of the human genome will revolutionize the way we think about human genetic variation, disease and evolution.”
