Twenty years ago, scientists announced that they had read a person's entire deoxyribonucleic acid (DNA), when, in fact, they missed a little. Now, thanks to improved methods of reading DNA, scientists can finally read the entire human genome from start to finish! According to reports, American scientists have sequenced 3.055 billion base pairs of the entire human genome. Compared with the previous results, the new results have added 200 million base pairs and more than 2,000 genes.
Humans have tens of thousands of genes, which are stored in DNA molecules, and the genetic information exists in the form of 4 bases (C, G, T and A), and the two bases pair with each other to form a base pair.
Scientists started the Human Genome Sequencing Project in 1990 and published the first draft of the human genome in 2001. But the genome had to be split into small reads and then reassembled, which couldn't put some of the highly repetitive pieces back in place. Geneticists have since continued to improve, but with a focus on improving the accuracy of existing sequences rather than adding new ones, about 8 percent of sequences are still missing or wrong.
The new version of the genome is mapped by the Telomere to Telomere (T2T) Consortium. The consortium is led by Karen Miga of UC Santa Cruz and Adam Philippi of the National Human Genome Research Institute.
The researchers chose to read DNA from a cell line called CHM13. The cell line is derived from a vesicular placenta—a condition of pregnancy failure—that can be grown in the lab. "What's unique about CHM13 is that it's not anyone's genome," Filippi said. The
average human cell has two copies of each piece of DNA, often with major differences, one from the mother and the other from the father, which makes Accurate sequencing of DNA has become more difficult because it is very tricky to figure out what is a mistake in the sequencing process and what is the real difference. Using CHM13 avoids this problem because the two copies are nearly identical.
To assemble the genome sequence, the research team used two technologies: one that can read very long (over 1 million base pairs) fragments; the other that is extremely accurate and can handle very small differences Fragments (such as multiple copies of the same gene) technology.
In July 2020, the team released the complete sex-determining human X chromosome. Now, they have released the complete human genome, with the new version adding nearly 200 million base pairs and 2,226 new genes over the previous version, the biggest improvement since the human reference genome was first published.
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