Genetics / deciphering the mammalian genome is essential for understanding human DNA * 75 million years ago the common ancestor of humans and mice lived
Tamara Traubman, Haaretz, via Walla!
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The scientists who decoded the human genome a year ago will today publish a decoded version of the mouse genome. The mouse, it turns out, has a similar number of genes as humans - about 30 thousand - and its genome is surprisingly similar to ours. "The mouse genome is essential to our understanding of the human genome, it shines a spotlight on all the things that have not been clarified from the human genome," said Dr. Kristen Linblad-To, head of the project in the USA, in a telephone interview with "Haaretz" from her office at the Whitehead Institute, Massachusetts .
Dr. Kristen Linblad-To, head of the project
"The achievement is a milestone in understanding our genome. This is the first time we have been able to compare, side by side, the human genome with the genome of another mammal," said Prof. Francis Collins, head of the National Institute for Human Genome Research, which funded a significant portion of both projects.
The great enthusiasm that the mouse genome arouses among biologists stems from the fact that the mouse is the most studied laboratory animal - there is almost no field in mammalian biology where the study of the mouse has not made a decisive contribution. "90% of the genes associated with diseases are similar in humans and mice," says Collins. "Already today, the mouse is used as a model for the study of many human diseases, and the list of genes we received today will help us create more accurate models, in a shorter time, and make progress in understanding the diseases."
The project to decipher the mouse genome began in 1999. The leaders of the project - scientists from the United States and England - set themselves the goal of finishing a draft of the mouse genome by . 2003 but last year the pace of work was accelerated, and additional research laboratories from Germany, Switzerland, France and other countries were added. On May 6, the project scientists deposited a draft of the sequence in GenBank, the website where all the sequenced DNA sequences are deposited; This site allows access to information for free. The research reports published today, in the scientific journal "Nature" include an analysis of the deposited data, including comparisons between the mouse genome and the human genome and insights gathered from a preliminary study of the two genomes.
Although the public project completed its task earlier than expected, already in June 2001, the private American genomics company Celera announced that it had finished deciphering a draft of the mouse genome. Researchers from the public project, made by scientists from universities and research centers funded by public funds, say that they are unable to know who achieved a better and more accurate sequence. "They didn't allow us access to their data," Linblad-To explained, "Celera only published one sample chromosome, and comparing it to our data, it seems to me that our sequence might be a little better." However, according to her, this is not the main question. "What's important," she says, "is that our data is available to everyone in the world. Celera's data is closed, and involves a payment to the company." The payment, according to Nature, is about NIS 210.
To decipher the mouse genome, the researchers used an approach known as the "genome-wide hunting gun": first they break down the entire genome into short DNA segments. After that, in the part called "decoding", identify the order of the DNA units that appear in each of the DNA segments. In the final stage - which is one of the critical stages in the method - advanced computer programs reassemble the segments into a complete sequence, according to overlapping parts at the ends of the segments.
The "Hunter's Gun" method was used by Dr. Craig Venter, former president of Celera, when the company competed in the public project to decipher the human genome. Scientists in the project mocked him at the time, saying that the method had indeed proven itself in bacteria, but there was no chance that it would work in larger mammalian genomes as well.
"Today, it is clear that the method works," says Dr. Ron Wades, a scientist from Bar Ilan University, who was also a partner in Celera's mouse genome project. Either way, the data published so far has already had a major impact on the research. "For the scientific community, the mouse genome is equal to the human one," said Prof. Alan Bradley, director of the Sanger Institute who participated in the project. According to him, "In recent months, the 'Ensemble' browser (a database that contains the decoding data) handled 2.6 million queries about detailed information from the mouse genome, compared to 3.2 million queries about the human genome." According to him, following the comparisons between the mouse genome and the human genome, about 1,200 new human genes have already been discovered.
Despite the visible differences between us and the mouse, the researchers discovered that at least 80% of the mouse's genes are similar to our genes. According to Prof. Eric Lander, director of the Whitehead Institute at the Massachusetts Institute of Technology and one of the partners in the project, the similarity stems from the fact that about 75 million years ago there lived a mammal, which was the common ancestor of man and mouse. Different lineages split from it, leading to the creation of the mouse and man. "Our shared genes are actually fossils embedded in our genome, an echo of our shared past," Lander said.
"The mouse genome provides a very important chapter in the book of evolution," Lander said. "The ability to read the book of evolution and compare the genomic information between the species will allow us to gain important information about ourselves; This is because evolution has preserved the most important genetic information in different species. If certain DNA sequences have been preserved by evolution for hundreds of millions of years, they must have an important role."
"There is no doubt that in terms of appearance and in aspects such as consciousness and language, we are very different from mice," says Dr. Wades, "but in terms of the molecular mechanisms that control our cells, we are actually quite similar." According to him, the biological differences are not due to the few genes unique to us or the mouse, "but because our genes are activated and expressed differently".
A concentration of life science experts, including the genome project
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