Posted on 06/04/2004 8:08:18 AM PDT by Michael_Michaelangelo
It is not often that the audience at a scientific meeting gasps in amazement during a talk. But that is what happened recently when researchers revealed that they had deleted huge chunks of the genome of mice without it making any discernable difference to the animals.
The result is totally unexpected because the deleted sequences included so-called "conserved regions" thought to have important functions.
All DNA tends to acquire random mutations, but if these occur in a region that has an important function, individuals will not survive. Key sequences should thus remain virtually unchanged, even between species. So by comparing the genomes of different species and looking for regions that are conserved, geneticists hope to pick out those that have an important function.
It was assumed that most conserved sequences would consist of genes coding for proteins. But an unexpected finding when the human and mouse genomes were compared was that there are actually more conserved sequences within the deserts of junk DNA, which does not code for proteins.
The thinking has been that these conserved, non-coding sequences must, like genes, be there for a reason. And indeed, one group has shown that some conserved regions seem to affect the expression of nearby genes.
To find out the function of some of these highly conserved non-protein-coding regions in mammals, Edward Rubin's team at the Lawrence Berkeley National Laboratory in California deleted two huge regions of junk DNA from mice containing nearly 1000 highly conserved sequences shared between human and mice.
One of the chunks was 1.6 million DNA bases long, the other one was over 800,000 bases long. The researchers expected the mice to exhibit various problems as a result of the deletions.
Yet the mice were virtually indistinguishable from normal mice in every characteristic they measured, including growth, metabolic functions, lifespan and overall development. "We were quite amazed," says Rubin, who presented the findings at a recent meeting of the Cold Spring Harbor Laboratory in New York.
He thinks it is pretty clear that these sequences have no major role in growth and development. "There has been a circular argument that if it's conserved it has activity."
(Excerpt) Read more at newscientist.com ...
Just for reference, mammals have ~3 billion basepairs, whereas insects have just 300 million.
Just for additional reference.
FROM:Database of Genome Sizes (DOGS)
ORGANISM Homo sapiens COMMON_NAME Human CLASSIFICATION eukaryota; metazoa; chordata; vertebrata; tetrapoda; mammalia; eutheria; primates. COMPLETED no GB_RELEASE 92.0 GB_ENTRIES 365804 GB_BASEPAIRS 154817348 GENOME_SIZE 3400000000 REF_TYPE 1 book REF_AUTHOR Wen-Hsiung Li REF_TITLE Molecular Evolution REF_PUBLISHER Sinauer Associates, Inc. REF_ADDRESS Sunderland, Mass., USA REF_PAGES 383 REF_YEAR 1997 ORGANISM Amoeba proteus COMMON_NAME Amoeba proteus CLASSIFICATION amoeba COMPLETED no GB_RELEASE GB_ENTRIES GB_BASEPAIRS GENOME_SIZE 290000000000 REF_TYPE 1 book REF_AUTHOR Wen-Hsiung Li REF_TITLE Molecular Evolution REF_PUBLISHER Sinauer Associates, Inc. REF_ADDRESS Sunderland, Mass., USA REF_PAGES 383 REF_YEAR 1997 // ORGANISM Amoeba dubia COMMON_NAME Amoeba dubia CLASSIFICATION amoeba COMPLETED no GB_RELEASE GB_ENTRIES GB_BASEPAIRS GENOME_SIZE 670000000000 REF_TYPE 1 book REF_AUTHOR Wen-Hsiung Li REF_TITLE Molecular Evolution REF_PUBLISHER Sinauer Associates, Inc. REF_ADDRESS Sunderland, Mass., USA REF_PAGES 383 REF_YEAR 1997
There does not seem to be correlation between the length of the genome and the size of the animal, just as with the number of chromosomes. Most bacteria have 5 - 30 million basepairs, but as you note the amoeba is a notable exception. Amoeba proteus at 300 billion isn't the largest, the organism with the longest genome is amoeba dubia with almost 800 billion basepairs. Virus genomes are measured in the thousands. Also, there are species of bat and deer with 50% - 70% of the length of most mammals. So the relationship between the size of the genome and the animal is unclear. Note I am not a biologist.
That is all I wanted to point out.
Genetic equivalent of WORKING-STORAGE in COBOL?
With ultra reliable storage device.
Subject to cratering by little Gamma ray thingies, unterminated array processing loops overlooked by God's Islamic programers distracted by virgins.
Spirits of undefiled women cause adverse genetic mutations.
Just because something doesn't work the way YOU would have designed it, doesn't mean it wasn't designed at all.
This chestnut is just the flip side of the creationist arguments on complexity.
The creationist says: It's too complex to have evolved.
The evolutionist says: It's too sloppy to have been designed.
Both suffer from subjectivism: the fallacy that your opinion is fact.
In the long run, no. In the short run, most certainly. Incorrect initial assumptions can totally screw up final results. It's happened again and again and again. In true science, the false assumptions generally self-correct as the final results become more and more at odds with reality.
However, scientists, like all humans beings, can be masters at self-denial and can carry on blindly in the face of contradictory results for decades.
Darwin's Radio by Greg Bear had a very interesting take on that feature. It's a good read.
If this is true, then we have another problem on our hands, specifically, the time it takes for evolution to occur. If there are redundant systems in DNA, then mutations will be that much, much less likely to manifest. The mutation would also have to compromise the redundant system in some way, or the mutation would simply be negated by the redundant system and repaired the next generation.
All science starts with a priori assumptions prior to evidence. Here's one from Physics:
Every point in the universe follows the same physical laws as the locally observable and testable environment.
There is no way to actually test this assumption experimentally, yet EVERY aspect of physics and astronomy is based on it as a foundational tenet.
You got it! Moreover, the regions contained by both mice and men are "pristine", not one mutation.
Thanks for the link.
There is no way to actually test this assumption experimentally
Say what? How much critical thought have you given this theory?
> If scientists would have approached the research from an ID perspective in the first place, they probably would never have coined such a term.
Indeed.
They wouldn't be scientists, either.
> the fact that they are ultra-conserved and seem to convey no survival advantage is a severe blow to RMNS
No, it isn't. It's quite simple: those genes that provide a benefit to the animal tend to be reproduced at a higher-than-normal rate. Those genes that are detrimental to the animal tend to be reproduced at a lower-than-normal rate. And those genes which simply do nothing at all are under no pressure to be deleted. Genes which are "off" will be left in place until such time as random replication errors cause changes, which may well be a very long time indeed.
ANALOGY ALERT: It's like computer programming, but without the programmer... as the program is updated, those sections of the code that are no longer needed might be tagged as "comments" and left in place.... they do nothing but sit there and take up a tiny amount of space. As several thousand generations of iterations occur, quite a lot of such "comments" can be built up; they do nothing, either good nor bad. If at some point the comments are deleted... the program runs just the same as it did when the comments were in place.
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