Molecular milestone: scientists unravel the human genome

[Hum]

In a milestone for the understanding of human genetics, scientists just announced the results of five years of work in unraveling the secrets of how the genome operates.

The ENCODE project, as it is known, dispensed with the idea that our DNA is largely "junk," repeating sequences with no function, finding instead that at least 80 percent of the genome is important.

The realization that traits and certain diseases can be passed from parent to offspring stretches back at least to the ancient Greeks, well before any genome was actually decoded. The Greek physician Hippocrates theorized that "seeds" from different parts of the body were transmitted to newly conceived embryos, a theory known as pangenesis.

What exactly these "seeds" might be was destined to remain a mystery for centuries. But the first person to put heredity to the test was Gregor Mendel, who systematically tracked dominant and recessive traits in his famous pea plants. Mendel published his work on the statistics of genetic dominance in 1866 to little notice.

But the painstaking work of cross-breeding pea plants wouldn't languish for long. In 1869, Swiss physician Johannes Friedrich Miescher became the first scientist to isolate nucleic acids, the active ingredient of DNA. Over the next several decades, scientists peering deeper into the cell discovered mitosis and meiosis, the two types of cell division, and chromosomes, the long strands of DNA and protein in cell nuclei.

In 1903, early geneticist Walter Sutton put two and two together, discovering through his work on grasshopper chromosomes that these mysterious filaments occur in pairs and separate during meiosis, providing a vehicle for mom and dad to pass on their genetic material.

With the link between chromosomes and heredity confirmed, geneticists delved deeper into the mysteries of the genome. In 1941, geneticists Edward Tatum and George Beadle published their work revealing that genes code for proteins, explaining for the first time how genes direct metabolism in cells. Tatum and Beadle would share half of the 1958 Nobel Prize in Physiology or Medicine for their discovery, which they made by mutating bread mold with X-rays.

In 1950, biochemist Erwin Chargaff figured out that the nucleotides, or building blocks, of DNA occur in specific patterns. These nucleotides are represented by four letters (A, T, G and C), and Chargaff was the first to discover that no matter the species, A and T always appeared in equal measures, as did G and C.

This discovery would be crucial to James Watson and Francis Crick, the scientists who would describe the structure of DNA for the first time in 1953. Combining Chargaff's work with studies by Maurice Wilkins and Rosalind Franklin and other scientists, the pair worked out the iconic double helix shape of DNA, a discovery Crick reportedly called "the secret of life."

In 1977, researchers sequenced a complete genome for the first time, starting with a rotund little bacteriophage known as Phi X 174. By 1990, science was ready to start something much bigger: a complete cataloguing of the human genome.

The result was the Human Genome Project, a 13-year international effort that resulted in the complete sequencing of the human genome in 2001.

Now, the ENCODE project has looked deeper into this "junk DNA" than ever before. And junk it is not: According to more than 30 research papers published today (Sept. 5) in a number of journals including Science and Nature, at least 80 percent of the genome is biologically active, with much non-protein-coding DNA regulating nearby genes in a complex dance of influence.

The findings reveal that the genetic basis of many diseases may not be in protein-coding genes at all, but in their regulatory neighbors. For example, genetic variants related to metabolic diseases pop up in genetic regions that activated only in liver cells. Likewise, regions activated in immune cells hold variants that have been associated with autoimmune disorders such as lupus.

"These breakthrough studies provide the first extensive maps of the DNA switches that control human genes," study researcher John Stamatoyannopoulos, associate professor of genome sciences and medicine at the University of Washington, said in a statement. "This information is vital to understanding how the body makes different kinds of cells, and how normal gene circuitry gets rewired in disease. We are now able to read the living human genome at an unprecedented level of detail, and to begin to make sense of the complex instruction set that ultimately influences a wide range of human biology."

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[Growled Member]

Interesting read. I've always suspected that most of our DNA wasn't junk at all, but needed information. Glad to see that verified.