When the scientists involved in the Human Genome Project published their first blueprint for the human genome in 2003, they knew ahead of time that:
- Coding segments (genes that define proteins) make up a small fraction of the total amount of DNA in each cell. We have about the same number of genes as mice (about 25,000), which is only 3% of the entire genome.
- The functions of the non-coding segments (i.e. the remaining 97%) were virtually unknown. Many called it "junk DNA"; they believed that this DNA was the wrongly copied and mutated remnants left behind by our ancestors over millions of years. Molecular taxonomists have used this "junk DNA" as a "molecular clockwork" - a tacit history of mutation that has not been influenced by natural selection for millions of years because this DNA has no function. Based on this idea, scientists have built many evolutionary stories of the origin of different types of life.
- Previously, genes were thought to be functional segments of a DNA molecule (exons) inserted between non-functional segments (introns) whose function is unknown. When a gene is read (copied, transcribed into RNA) and then translated into protein, the introns are spliced out and exons are glued together to produce a functional gene.
- Copying (transcription) of a gene begins at a specially designated place (START), and ends at a special place designated STOP.
- Gene switches (molecules called transcription factors) are placed on the chromosome near the site of the START gene.
- Transcription occurs in one direction, from the START to the end of the STOP.
- Genes are scattered along the entire length of chromosomes, like beads on a string, although some areas contain more genes than others.
- DNA is made up of two twisted spirals, something like a twisted zipper. One strand of DNA complements the other, like the sides of a clasp. Previously, it was believed that only one side of the DNA "buckle" (called the "sense" strand) provides the correct sequence for proteins. The extra strand is called a "nonsense" strand. It was assumed that protein formation (with the exception of rare exceptions) occurs only as a result of reading the sense strand without any involvement of the non-sense strand. At the same time, the nonsense chain, according to scientists, plays the role of a template for copying the semantic chain, just as a photo-negative is used to form a photograph.
A cell probably uses the entire genome, and there is no such thing as junk DNA.
Now this whole structure of DNA knowledge has been turned upside down. The recently implemented ENCODE project reported the results of a thorough study of transcripts (copies of RNA made from DNA) of just 1% of the human genome. Their discoveries include the following:
- Approximately 93% of the genome is read (not 3% as expected). Further research can increase this figure to 100%. Since transcription requires a lot of energy and perfect consistency, this means that the cell probably uses the entire genome and there is no such thing for a molecule as "junk DNA".
- Exons are not gene-specific (related to genes) but are modules that can bind to many different RNA transcripts. One exon (i.e., one part of one gene) can be used in combination with up to 33 different genes located on 14 different chromosomes. This means that one exon can encode one part that is used by many different proteins.
- The genes are not arranged in a line like “beads on a string”, but rather have a layered structure of partially overlapping segments. With this structure, 5, 7, 9 or more transcripts are derived from one "gene".
- Not one, but both strands (semantic and non-semantic) of the DNA molecule are fully read (transcribed).
- Transcription takes place not only in one direction - it goes back and forth (!).
- Transcription factors can be tens or hundreds of thousands of base pairs (nucleotides from) of the gene they control, even on different chromosomes.
- There is not one START place, but many, and they are located in each gene region.
- For each area, there is not one read triggering system, but a whole series.
The authors conclude the following:
"These results are so amazing and shocking, and therefore it will take us much longer to understand the processes that actually occur in cells."
This concern for the safety of so many RNA molecules produced in such a small space is well-founded. RNA is a single-stranded molecule, somewhat like duct tape, as it sticks to any nearby surface, including itself! And if the process is not clearly coordinated, all RNA will simply crumple and turn into a sticky mass.
And taxonomists and molecular biologists, who have come up with many evolutionary histories ("phylogenesis") of the development of organisms, have no choice but to leave these reconstructions, created over many years on the basis of the idea of "junk DNA", and wait for the manifestation of all the consequences of this discovery, in order try to redo everything.
One of the supposedly “strong” arguments for the fact that humans have an ancestor in common with chimpanzees is the presence of a common “non-functional” DNA. As you can see, this argument just flew into the pipe, losing all meaning.
Promotional video:
Alexander Williams
