Researchers Find 'Junk DNA' May Have Triggered Key Evolutionary Changes in Human Thumb and Foot

Sep 04, 2008
Researchers Find 'Junk DNA' May Have Triggered Key Evolutionary Changes in Human Thumb and Foot
A rapidly evolving sequence from the human genome drives gene activity in the developing thumb, wrist and ankle of mouse embryos.

(PhysOrg.com) -- Out of the 3 billion genetic letters that spell out the human genome, Yale scientists have found a handful that may have contributed to the evolutionary changes in human limbs that enabled us to manipulate tools and walk upright.

Results from a comparative analysis of the human, chimpanzee, rhesus macaque and other genomes reported in the journal Science suggest our evolution may have been driven not only by sequence changes in genes, but by changes in areas of the genome once thought of as "junk DNA."

Those changes activated genes in primordial thumb and big toe in a developing mouse embryo, the researchers found.

"Our study identifies a potential genetic contributor to fundamental morphological differences between humans and apes," said James Noonan, Assistant Professor of Genetics in the Yale University School of Medicine and the senior author of the study.

Researchers have long suspected changes in gene expression contributed to human evolution, but this had been difficult to study until recently because most of the sequences that control genes had not been identified. In the last several years, scientists have discovered that non-coding regions of the genome, far from being junk, contain thousands of regulatory elements that act as genetic "switches" to turn genes on or off.

An indication of their biological importance, many of these non-coding sequences have remained similar, or "conserved," even across distantly related vertebrate species such as chickens and humans. Recent functional studies suggest some of these "conserved non-coding sequences" control the genes that direct human development.

In collaboration with scientists at Lawrence Berkeley National Laboratory in California, the Genome Institute of Singapore, and the Medical Research Council in the United Kingdom, Noonan searched the vast non-coding regions of the human genome to identify gene regulatory sequences whose function may have changed during the evolution of humans from our ape-like ancestors.

Noonan and his colleagues looked for sequences with more base pairs in humans than in other primates. The most rapidly evolving sequence they identified, termed HACNS1, is highly conserved among vertebrate species but has accumulated variations in 16 base pairs since the divergence of humans and chimpanzees some 6 million years ago. This was especially surprising, as the human and chimpanzee genomes are extremely similar overall, Noonan said.

Using mouse embryos, Noonan and his collaborators examined how HACNS1 and its related sequences in chimpanzee and rhesus monkey regulated gene expression during development. The human sequence activated genes in the developing mouse limbs, in contrast to the chimpanzee and rhesus sequences. Most intriguing for human evolution, the human sequence drove expression at the base of the primordial thumb in the forelimb and the great toe in the hind limb. The results provided tantalizing, but researchers say preliminary, evidence that the functional changes in HACNS1 may have contributed to adaptations in the human ankle, foot, thumb and wrist-- critical advantages that underlie the evolutionary success of our species.

However, Noonan stressed that it is still unknown whether HACNS1 causes changes in gene expression in human limb development or whether HACNS1 would create human-like limb development if introduced directly into the genome of a mouse.

"The long-term goal is to find many sequences like this and use the mouse to model their effects on the evolution of human development," Noonan said.

Provided by Yale University

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Icester
3 / 5 (1) Sep 05, 2008
I'm not trying to start a huge argument, but could someone please answer the following questions regarding evolution?

(1) Where are all the "in-betweens"? You know, those evolved animals that aren't quite there yet? Shouldn't the world be flooded with a wide degree of these since evolution takes millions to billions of years? Logic dictates that there should practically be a continuum of evolution "states" from one species to the next.

(2) How does evolution account for mutations crossing the species line in which involve different numbers of chromosomes? Every chromosomal defect I've ever heard of (caused by too many or missing chromosomes) results in a non-viable animal. Or in the best case, a weakened animal that is usually unable to reproduce.

(3) What is the mathematical probability of the following circumstances:
(a) mutation results in a positive mutation
(b) mutation results in an animal that can reproduce
(c) enough mutated animals occur to create a self-sustaining population This requires that (1) the animals are geographically close and (2) animals are chronologically close so that they are within breeding age

Thanks
zevkirsh
4 / 5 (1) Sep 05, 2008
junk dna is anything but junk. it is a testament to scientific arrogance that what we do not understand we call junk. no, if anything, nature conserved it there for us to observe because it is treasure, not junk. i recall in 1997 telling my advanced placement biology teacher in high school that calling it junk dna made no sense and that is was obvious that it was there for a reason and was both necessary and full of more information we could not yet decipher.....
ofidiofile
not rated yet Sep 05, 2008
I'm not trying to start a huge argument, but could someone please answer the following questions regarding evolution?


the answers are out there, but if you're asking for simple one-liners that will fit in a comment box, you're out of luck.

1)natural selection has no goals -- it is NOT a conscious process -- species evolve in response to changes in their environment so as to be able to continue to survive and reproduce. that is all. as for transitionals, to make any claims about present-day "missing links" is to claim to have knowledge of the future (i.e., you'd have to know what it was "turning into"). transitional species only appear in hindsight, by defintion.

2)look up the red viscacha-rat, which is tetraploid [4n] (nearly double the chromosomes of its closest relative). somewhere down the line, its ancestors were born with double the normal number of chromosomes, though losing the sex chromos and a few others (which prevented what would otherwise be lethal effects).

i suspect you're a creationist (i know the signs, having been raised one myself), but i'll grant you the benefit of the doubt. if you're honest in that you are actually curious (i.e., you're not just a troll), you can go here:

http://www.talkor...indexcc/

browse around. i've heard your questions before, many more times than i care to recall.

if, however, you are a dyed-in-the-wool creationist, there are no facts in existence that will change your mind, and no one anywhere who will be able to give reasonable answers to your questions.

i hope you find what you're looking for.
HenisDov
3 / 5 (1) Sep 06, 2008
Extra, Extra Read All About It !
Researchers Uncover DNA Mystery !


A. Mystery uncovered!

Yale researchers:" 'junk DNA' may have triggered...evolution of..."

http://www.eureka...0208.php

"... evolution may have been driven not only by sequence changes in genes, but by changes in areas of the genome once thought of as "junk DNA"..."


B. Mystery uncovered?

NO NO NO

DNA does not "trigger" nor drive anything.

DNA is a component of life's prime organism, the gene. The gene, the organism, is "driven" to acquire new capability. The driver is the ubiquitous biological entity, culture.


C. Mystery uncovered. Evolution recomprehended.

Genes, Earth's primal organisms even when they are interdependent members of their genome communal cooperative, evolve in response to their survival requirements, which are THEIR CULTURE.

Darwinism starts with pre-Archaea individual independent genes, their evolution driven by their culture.

From http://blog.360.y...Q--?cq=1]http://blog.360.y...Q--?cq=1[/url]&p=409

- Genes are organisms, interdependent members of genes communes, genomes, all continuously undergoing evolution directed towards survival as long as possible, for maintaining Earth's biosphere as long as possible, which is the reason and purpose of their, and our, existence.

- Culture is a ubiquitous biological entity and is the major effector of genetic evolution, of capabilities and attributes selected for survival.

- The major course of natural selection is NOT via random mutations followed by survival, but via interdependent, interactive and interenhencing selection of biased replication routes by genes at their alternative-splicing-steps junctions, effected by the cultural feedback of the 3rd stratum celled organisms to their 1st stratum genes organisms via their 2nd stratum genome organisms.


Dov Henis

http://blog.360.y...Q--?cq=1]http://blog.360.y...Q--?cq=1[/url]&p=372

Puzzled why even Darwinians do not comprehend that Darwinism starts all the way back with Life's day one, with the pre-archaea not-yet-genomed-celled genes...