How zebrafish mutation guides species to extinction instead of theoretical improvement despite, evolutionary propaganda attempts
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[__ Science __ ] Fins to Limbs?
- Thread starter AIG.com
- Start date
Barbarian
Member
Not surprisingly, AIG got this one completely wrong. The zebrafish is a highly evolved teleost, and would not be a candidate for producing tetrapods. However, the developmental genes for doing that still remain in place in the zebrafish genome.
What's remarkable is that a single mutation produces both bone and muscle changes that are necessary to produce tetrapods:
Researchers, led by M. Brent Hawkins, a recent doctoral recipient in the Department of Organismic and Evolutionary Biology, performed forward genetic screens in zebrafish looking for mutations that affect the fin skeleton. Unlike tetrapod limbs, which have complex skeletons with many bones that articulate at many joints, zebrafish pectoral fins have a simple endoskeleton that lacks joints. To their surprise, Hawkins and colleagues found mutants that modified their fins into a more limb-like pattern by adding new bones, complete with muscles and joints. These results reveal that the ability to form limb-like structures was present in the common ancestor of tetrapods and teleost fishes and has been retained in a latent state which can be activated by genetic changes.
...
Histological analysis revealed that the new bones had muscle attachment, which occurs extensively in limb bones, but not in the fin. In teleost fishes there are no muscles attached to the bones. Instead, the bones provide an intermediate support in the fin and the muscles extend directly from the shoulder out to the bony fin rays, bypassing the bones all together. The new bones are fully integrated into the fin, complete with joints for articulation and attachment to the fin muscles.
Much work has been done in the field of limb development and it provides a good understanding of what genes are present and required to make the limb form. In this study however, researchers flipped traditional approaches by focusing on the small simple zebrafish fin and asking what genetic changes could elaborate the appendage and increase its complexity. "Prior to this there aren't any examples where we have genes or mutations that actually elaborate the structure and make it even more complicated," said Hawkins. "Even in the case of limbs we only know how to make a limb smaller or less complex, but we didn't have any information on how add elements to a fin or a limb."
"That was very surprising as well," confirmed Harris. "We had no hard experimental examples where you take a gene, turn it up, make it work more and get a more complex mature structure at the end. In our findings we actually found some of the dials that can turn up the genetic pathways and get a more complicated structure in the end."
This finding also fits well with another recent discovery that Hox13 genes are required to form the distal regions of both fins and limbs. Altogether these discoveries reveal that the appendage Hox code was likely present in the common ancestor of tetrapods and teleost fishes and is not specific to the tetrapod lineage.
This study shows that both fins and limbs use the same genetic mechanisms to specify the middle portion of the appendage.
phys.org
The zebrafish has evolved a long way from the ancient ancestors of lobe-fined fish. But the genes for making legs are still there.
What kind of "designer" would put instructions for making an ulna and a radius, and all the necessary muscles in a fish? Not a very good "designer." But an omnipotent Creator, Who uses nature to create new kinds of organisms, would certainly have done that.
What's remarkable is that a single mutation produces both bone and muscle changes that are necessary to produce tetrapods:
Researchers, led by M. Brent Hawkins, a recent doctoral recipient in the Department of Organismic and Evolutionary Biology, performed forward genetic screens in zebrafish looking for mutations that affect the fin skeleton. Unlike tetrapod limbs, which have complex skeletons with many bones that articulate at many joints, zebrafish pectoral fins have a simple endoskeleton that lacks joints. To their surprise, Hawkins and colleagues found mutants that modified their fins into a more limb-like pattern by adding new bones, complete with muscles and joints. These results reveal that the ability to form limb-like structures was present in the common ancestor of tetrapods and teleost fishes and has been retained in a latent state which can be activated by genetic changes.
...
Histological analysis revealed that the new bones had muscle attachment, which occurs extensively in limb bones, but not in the fin. In teleost fishes there are no muscles attached to the bones. Instead, the bones provide an intermediate support in the fin and the muscles extend directly from the shoulder out to the bony fin rays, bypassing the bones all together. The new bones are fully integrated into the fin, complete with joints for articulation and attachment to the fin muscles.
Much work has been done in the field of limb development and it provides a good understanding of what genes are present and required to make the limb form. In this study however, researchers flipped traditional approaches by focusing on the small simple zebrafish fin and asking what genetic changes could elaborate the appendage and increase its complexity. "Prior to this there aren't any examples where we have genes or mutations that actually elaborate the structure and make it even more complicated," said Hawkins. "Even in the case of limbs we only know how to make a limb smaller or less complex, but we didn't have any information on how add elements to a fin or a limb."
"That was very surprising as well," confirmed Harris. "We had no hard experimental examples where you take a gene, turn it up, make it work more and get a more complex mature structure at the end. In our findings we actually found some of the dials that can turn up the genetic pathways and get a more complicated structure in the end."
This finding also fits well with another recent discovery that Hox13 genes are required to form the distal regions of both fins and limbs. Altogether these discoveries reveal that the appendage Hox code was likely present in the common ancestor of tetrapods and teleost fishes and is not specific to the tetrapod lineage.
This study shows that both fins and limbs use the same genetic mechanisms to specify the middle portion of the appendage.
Can a fin become a limb? Single mutations cause zebrafish fins to transform into complex limb-like structures
Fin-to-limb transition is an icon of key evolutionary transformations. Many studies focus on understanding the evolution of the simple fin into a complicated limb skeleton by examining the fossil record. In a paper published February 4 in Cell, researchers at Harvard and Boston Children's...
The zebrafish has evolved a long way from the ancient ancestors of lobe-fined fish. But the genes for making legs are still there.
What kind of "designer" would put instructions for making an ulna and a radius, and all the necessary muscles in a fish? Not a very good "designer." But an omnipotent Creator, Who uses nature to create new kinds of organisms, would certainly have done that.
Truthfrees
Member
thanks - great points
Barbarian
Member
The result that AIG declared to be impossible:
Hawkins and his colleagues discovered a mutant zebrafish with an unusual pair of additional bones at the base of its pectoral fins. The bones are integrated into the rest of the fish’s body, forming what the scientists call a limb-like joint, replete with muscle connections. The bones sit awkwardly below the zebrafish’s fins, pushing up one end of the entire structure.
But what really makes these out-of-place bones important is how they got there and what that may mean for the evolution of limbs.
Hundreds of millions of years ago, fish effectively split into two lineages: ray-finned fish and lobe-finned fish. Ancient members of the lobe-finned group (which includes the serious-looking coelacanth and all lungfish species) later evolved into species with limbs. The ray-finned fish went their own way and never evolved limbs.
The extra bones discovered in the mutant zebrafish, known as “intermediate radials,” are commonly found in four-limbed species, tetrapods, albeit in a larger and more useful form. But a zebrafish is a ray-finned fish: there is no sense in these extra bones being there. The fact that they are says something very interesting.
...
According to the work of Hawkins and his colleagues (which has not yet been peer reviewed), the development of the mutant bones in the zebrafish appears to be regulated by the same group of genes—HOX11—that regulate the development of forearm bones in tetrapods, including humans.
Zebrafish may be ray-finned fish, but they share a distant ancestor with lobed fish. Discovering that the HOX11 gene triggers the development of nascent limb-like structures is like reactivating a 400-million-year-old genetic sequence.
This confirms evidence of the gradual evolution of tetrapods. As YE creationist Kurt Wise says, the tetrapod series of fossils is:
Evidence for not just one but for all three of the species level and above types of stratomorphic intermediates expected by macroevolutionary theory is surely strong evidence for macroevolutionary theory.
There is "strong evidence" for the evolution of tetrapods in the fossil record, and now we have direct genetic evidence confirming the fossil series.
Hawkins and his colleagues discovered a mutant zebrafish with an unusual pair of additional bones at the base of its pectoral fins. The bones are integrated into the rest of the fish’s body, forming what the scientists call a limb-like joint, replete with muscle connections. The bones sit awkwardly below the zebrafish’s fins, pushing up one end of the entire structure.
But what really makes these out-of-place bones important is how they got there and what that may mean for the evolution of limbs.
Hundreds of millions of years ago, fish effectively split into two lineages: ray-finned fish and lobe-finned fish. Ancient members of the lobe-finned group (which includes the serious-looking coelacanth and all lungfish species) later evolved into species with limbs. The ray-finned fish went their own way and never evolved limbs.
The extra bones discovered in the mutant zebrafish, known as “intermediate radials,” are commonly found in four-limbed species, tetrapods, albeit in a larger and more useful form. But a zebrafish is a ray-finned fish: there is no sense in these extra bones being there. The fact that they are says something very interesting.
...
According to the work of Hawkins and his colleagues (which has not yet been peer reviewed), the development of the mutant bones in the zebrafish appears to be regulated by the same group of genes—HOX11—that regulate the development of forearm bones in tetrapods, including humans.
Zebrafish may be ray-finned fish, but they share a distant ancestor with lobed fish. Discovering that the HOX11 gene triggers the development of nascent limb-like structures is like reactivating a 400-million-year-old genetic sequence.
This confirms evidence of the gradual evolution of tetrapods. As YE creationist Kurt Wise says, the tetrapod series of fossils is:
Evidence for not just one but for all three of the species level and above types of stratomorphic intermediates expected by macroevolutionary theory is surely strong evidence for macroevolutionary theory.
There is "strong evidence" for the evolution of tetrapods in the fossil record, and now we have direct genetic evidence confirming the fossil series.