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Human Gene Count Slashed
jd continues: "This has the potential for making life extremely interesting for genetic engineers, given that both individual genes and interactions between genes must be proportionately more complex, in order to get the same level of complexity out. Half the number of genes equates to twice the information encoded in forms other than discrete physical blocks of code.
There is no mention in the article of a story running in 2002 of genetic therapies unexpectedly causing cancer, although if you now factor in the increased complexity of interactions, it is possible that such side-effects can be better understood and therefore prevented. The new estimates, therefore, are more than just idle curiosity but have the potential for impacting how the science is approached."
It is the number of genes that has been revised down. The genome is the complete set of DNA and contains all the genes.
Gauging the complexity is difficult, given there are a number of factors not currently understood, particularly the importance of non-coding RNA, which accounts for 98% of the genome. In the past, the information content of these regions was thought to be low, but this attitude is changing. As knowledge of the genome increases, the estimated number of genes drops, and more information emphasis is put on non-coding portions of the genome.
Evaluating the function of ncRNA is difficult because as of yet there are no statistically significant markers for them. Given the release today, and trends of late, more and more attention will be put on trying to decipher the utility of "junk" DNA.
to how many genomes are in a single human genome. However, speaking about genes in a genome, as the article states, this "correction" only counts those genes that make some discernable protein product. The number misses the number of open reading frames (ORF) that may not encode a protein at all, but a regulatory or enzymatic RNA. Probably, the next big project in life/medical research, after the big proteomics initiatives, will be the study of non-protein encoding ORFs. This problem is very tough to crack since 1) these RNA's do not have a common sequence element like "normal" messenger RNAs, 2) may be as short as 15 base pair (LIN12(?) in C. elegans), and 3) there are MANY, MANY possible ORFs in the genome.
Are these technically genes? They are regulated. They have a function. They are transcribed. The only thing different from the standard definition of a gene is that the RNA is not translated into protein.
In addition to multiple protein products from one "gene" as the article states, regulation of the gene may also be much more complex compared to "lower" organism. For example, the gene expression profile of the malarial parasite Plasmodium falciparum suggests very limited regulation. Basically, it looks like a linear progression with very limit amount of response. So, temporal and spatial regulation makes even multiple product genes seem to like a larger cohort of genes. Take the daughterless gene in Drosophila. It is used very early in embryonic development to control sexual differentiation. However, later, the gene product is used in neuronal differentiation. So, for the fly, sex is literally on the brain.
The thing is, we've had the arabidopsis genome sequenced for a while now. And because the organism has a lower degree of complexity it is a lot easier to study in many ways. I don't know if I'd necessarily say that there is more study being done on humans than on Arabidopsis - In fact, I highly doubt it.
We have a much clearer idea of most of the inner workings of that lowly little mustard plant than of our own. It's a matter of understanding the simple stuff and then working our way up. Like with the nematode C. elegans -- we know more information about that than you could possibly imagine. We know how many cells it has at every stage of its life and what they are doing. We have its genome sequenced. And from all of this information we have learned a lot about the inner workings of our cells as well. You find a lot of homologies between organisms.
In fact, if you examine the RNA polymerases of humans, bacteria and archaea you would find that ours are much closer to archaea (the most ancient of ancient organisms still around) than to bacteria.
So looking at these organisms that have been around since the beginning of life, we can learn about the development of our genomes and by examining their functions we can learn much about how ours work. Even if we do have our entire genome sequenced, that doesn't mean we know what it all does.
Actually last months Scientific American had a good article on this. Basically we are finding that what we once thought was junk (non coding areas and RNA coding areas which do not code for proteins) is probably some of the more important aspects of the nucleus. I quote:
"But investigators have since sequenced the genomes of diverse species, and it has become abundantly clear that to correlation between numbers of conventional genes and complexity truly is poor. The simple nematode worm Caenorhabditis elegans (made up of only about 1,000 cells) has about 19,000 protein-coding genes, almost 50 percent more than insects (13,500) and nearly as many as humans (around 25,000). Conversely, the relation between the amount of nonprotein-coding DNA sequences and organism complexity is more sonsistent.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
Only one? Ahem: Mitochondrial genome; Nuclear genome.
:)
As a mitochondrial researcher, I resent the most important organelle of the cell being overlooked or lumped in together with the nucleus here!
So I would say two genomes