A new study conducted by a group of researchers from MIT and Harvard University and published in the journal PNAS, estimates that the number of human genes is a few thousand smaller than commonly thought, and stands at about 20,500 genes
How many genes does a person have? The genetic information in living things is encoded by DNA molecules. The DNA molecules are long chains consisting of four building blocks (nucleotides marked with the letters A, T, G and C). These chains contain gene sequences called ORFs (open reading frames), which, for the most part, are translated by the cell into proteins. In addition, DNA contains sequences that do not code for genes.
Since the completion of the human genome project, which was first published in 2001, and within the framework of which the human DNA sequence was determined, there have been various estimates regarding the number of genes. Identifying the genes that code for proteins versus regions that do not contain genes is not a simple task. The method used by many researchers to identify genes that code for proteins is by finding sequences in the genome that contain at the beginning and at the end elements that define ORFs (that is, sequences that mark the beginning and end of the gene, and are at a reasonable distance from each other).
As of today, it is estimated that there are about 24,500 genes in a person. However, many questions about the correctness of this number arose following the publication of the mouse genome sequences in 2002. From an evolutionary point of view, since genes code for proteins, and usually perform essential biological functions, they are not expected to undergo major changes between different mammals. But, surprisingly, a comparison between the two genomes shows that there are many ORFs that have been identified in humans and do not appear in mice, and vice versa. The problem is that without practical tools to identify "real" genes, the databases and computerized catalogs contain sequences of ORFs that do not code for proteins, and cannot be identified and removed.
In a study led by Prof. Eric Lander and Michele Clamp, a method was developed which is based on the principle of the conservation of genes during evolution. The researchers determined that genes are valid if there are similar sequences in other mammals as well. Therefore, the researchers compared the ORFs from humans with those from the mouse and dog genomes. They found that there are over 1100 "orphan" ORFs that look like genes but do not exist in other mammals.
Regarding the "orphan" ORFs, which are unique to humans - they may have existed in other animals but degenerated in them during evolution, or alternatively, they are new genes that were "invented" in primates (that is, in humans and monkeys). In any case, the researchers expected that if indeed they are genes that code for proteins, they would also appear in monkeys. In order to test this possibility, the researchers made a comparison between the human genome and that of the chimpanzee and the macaque. They found that the great majority of them were not similar to genes in monkeys, and were apparently random sequences that do not code for proteins.
Even when they searched the professional literature for clues to the existence of proteins encoded by the "orphan" ORFs, they found almost no evidence supporting their existence. Hence, the vast majority of the ORFs that do not have a counterpart in other species do not represent genes. Therefore, if a gene is found that is not evolutionarily conserved, actual experimental evidence must be collected before it can be treated as a coding sequence and added to the databases as an ORF.
According to this method of comparing genomes, it is possible to create a new catalog of genes that code for proteins in different animals, and at the same time create catalogs containing the sequences that do not have a protein product and try to stand for their role and importance.
According to Klemp, there is very little innovation when it comes to genetic variation among mammals. According to her, the number, structure and function of the genes coding for proteins is not expected to change radically between different mammals. This research raises a fundamental question about what are the elements in the genome that define us as people and differentiate us from the mouse, the dog and other mammals.
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The number of genes you presented are in one cell of a person and not in the whole body. Need to be precise.
The information should be accurate. This is a number of genes in one cell in the human body. Not in the whole human body.
In introspection I counted 26 thousand genes.
The question is: how do you define a garden?
Today it is known that many of the ORFs are not translated into protein at all but only copied into RNA. Is a gene just a sequence that undergoes translation and becomes a protein? And if the protein does not carry out processes in the body, is it still a "gene"? And what about miRNA and its other friends?
If the whole function of the "gene" is actually to slow down other processes in the cell by seizing proteins that are responsible for translation or TFs?
There are many problems in defining a garden. If today they had to redefine the genomic world, they would make completely different decisions and not call every "gene" a gene (among other things).
And for the cool commenter - this will never happen. Even in identical twins, there is no complete match. This is mainly due to random processes both in the embryo and in subsequent development.
Thanks.
Absolutely not, I must have mistakenly clicked on the square that indicates not to give a response option.
A question for my father, why is it not possible to post comments on the article "IBM presents a new technology that will enable a supercomputer on one tiny chip"? Is there a justified reason for blocking the comments in the above article?
Perhaps the 1100 ORF sequences unique to man that do not exist in any other mammal were implanted in apes tens of thousands of years ago by an advanced alien culture and thus man was created.
The most beautiful day is the day when they can describe a human being based on his DNA. (General appearance, diseases and tendencies towards them, character such as tendency to irritability or weak long-term memory, etc.)