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The Gene Is Having an Identity Crisis
gollum123 writes "New large-scale studies of DNA are causing a rethinking of the very nature of genes. A typical gene is no longer conceived of as a single chunk of DNA encoding a single protein. It turns out, for example, that several different proteins may be produced from a single stretch of DNA. Most of the molecules produced from DNA may not even be proteins, but rather RNA. The familiar double helix of DNA no longer has a monopoly on heredity: other molecules clinging to DNA can produce striking differences between two organisms with the same genes — and those molecules can be inherited along with DNA. Scientists have been working on exploring the 98% of the genome not identified as the protein-coding region. One of the biggest of these projects is an effort called the Encyclopedia of DNA Elements, or 'Encode.' And its analysis of only 1% of the genome reveals the genome to be full of genes that are deeply weird, at least by the traditional standard of what a gene is supposed to be and do. The Encode team estimates that the average protein-coding region produces 5.7 different transcripts. Different kinds of cells appear to produce different transcripts from the same gene. And it gets even weirder. Our DNA is studded with millions of proteins and other molecules, which determine which genes can produce transcripts and which cannot. New cells inherit those molecules along with DNA. In other words, heredity can flow through a second channel."
I'd venture a guess that it's not correct (simply not enough evidence supporting it, but that has not yet been ruled out either.
The bottom line is that we do not yet fully understand memory, in much the same way that we do not fully understand synapse formation in the brain. We should just wait and see before jumping to any conclusions (and maybe write a grant proposal or two along the way).
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I recall people freaking out when the human genome project revealed that Humans only have about 30,000 genes rather than the previous estimate of 150K.
It always seemed to me that measuring Human complexity based on the number of our genes is a little like judging a book by the number of words it contains. It completely ignores the fact that words have Meaning.
Poetry is both the most compact and the most subtle form of written expression.
This latest finding suggests to me that something similar applies to our genetic heritage.
-S
I recall people freaking out when the human genome project revealed that Humans only have about 30,000 genes rather than the previous estimate of 150K.
It always seemed to me that measuring Human complexity based on the number of our genes is a little like judging a book by the number of words it contains. It completely ignores the fact that words have Meaning.
Uh, I remember when they discovered that too, and I don't recall any scientists "freaking out" because the low number of genes implied we had low "complexity". Instead, I remember them being very excited, because they already knew there are far more than 30,000 proteins generated from our DNA, meaning that the 1:1 gene:protein mapping theory had to be wrong, and the mechanism was far more complicated than previously thought.
This sounds to me like a continuation of the line of inquiry opened by that discovery years ago, where now they're gaining a better idea of how the genes really code for proteins. With the extremely interesting aspect that some of this is controlled by things not part of the DNA itself, yet which can still be inherited.
To (ab)use your analogy, if the human body is a work of literature then proteins are the words, and genes are characters. The number of words hasn't changed, it's just that before we thought the language was like Chinese, where a single character mapped to a single word. Now we realize it's more like English, where the interactions between characters create different words. Oh and now we've discovered that there's also punctuation like apostrophes and hyphens which can significantly alter the meaning of the resulting words.
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Some of it is new, but none of it is surprising to anyone who has been paying attention for, I dunno, the past decade.
It's been clear since the mid-90's when we learned that there were only 44k "coding" genes but at least ten times that many proteins that more was going on than simple templating.
Things like methylation of double-stranded DNA have been known to be important in oncogenesis for at least ten years. miRNAs have been considered important for five years or more. Other conserved non-coding regions have been known for almost as long or longer.
This story is going to be like that "green" story that reports breathlessly every year or so that some company has instituted green policies because they save money! Just like Interface did fifteen years ago, and hundreds of others have done since.
The interesting thing is that these persistently "new" stories give us a measure of how slowly what can fairly be called "general knowledge" changes. Based on evidence from the "green" story we can expect to be hearing the AMAZING NEWS that there's more to genes than template coding until at least 2020.
Following the details as we learn them is fascinating. Being told that an uncontroversial fact we've known for a decade or more is "news" is very, very irritating.
Blasphemy is a human right. Blasphemophobia kills.
I think what you are referring to is more closely related to instinct than memory. Instinct is related to sets of behaviors that are performed naturally, learned. These are to some extent controlled by genes, but can be overridden by learning. I.E. genes will encode for certain basic neural pathways to be formed, but the brain's development will then be left to augment or diminish that pathway's strength.
Memory is an entirely different system, in which patterns simulating previous stimuli are stored and available to be replayed or compared against. Calling the effect of instinct "ancestral memory" or "genetic memory" is at best a poetic interpretation, at worst a logical flaw similar to Lamarkian Evolution wherein giraffes have long necks because their ancestors stretched out trying to graze from tall shrubs, then trees, rather than the Darwinian idea that giraffes have long necks because short necked giraffes did not live to reproduce as well as long necked ones.
I'll never make that mistake again, reading the experts' opinions. - Feynman
Raising both a two year old and a seven month old, there appears to be precious little instinct. Maybe dancing to music.
GPL Deconstructed
>>The way I understand it is that a large part of evolutionary theory ASSUMES that memory can't be inherited.
Maybe not memory per se, but certain phenomena have demonstrated Lamarckian style inheritance.
Mm, DNA can be methylated, which modifies its behavior. A fat pregnant mother will methylate the genes in the fetus, resulting in a kid much more genetically prone to being fat. Experiments with dutch prisoners of war during WWII showed that even when raised under similar conditions, kids from mothers who ate more when they were pregnant were much more prone to obesity.
There's also effects like http://en.wikipedia.org/wiki/Genomic_imprinting which modify an offspring's genome on the fly between generation and generation.