Introduction
In the article, Making Limbs from Fins, Scheider and Shubin investigate the genetic transformations involved in the evolution of fish fins into limbs. The findings support the views presented by paleontologist Jenny Clack in the video, Evolution: “Great Transformations”. Clack studied tetrapods structures and found evidence supporting the development of limbs from fish fins. The researchers also acknowledged the validity of genetic clues presented by Hogenboom in the article, Genetic clue to how limbs evolved from fins.
Article Review
The research evaluates the possibility of using the transformation genetics of fish fins to develop new limbs on a fish (Scheider et al. 1121). The researchers claim that the Devonian period culminated in the realization of two noteworthy innovations that led to the formation of the tetrapod limbs. The theoretical framework is enhanced using studies published by credible researchers. The article focuses on the structure of fin rays, which are subject to the transformations of the apical ectodermal ridge (AER). Secretions from the AER are responsible for limb proximodistal growth. However, the growth is suspended during digit patterning in order to form fin folds. Schneider et al. consider 5’Hoxd gene expression extensively responsible for digit formation (1121). The article predicts that the second phase of 5’Hoxd gene expression may help in explaining the origin of the autopod. Additionally, emphasis is placed on a study conducted by Freitas and colleagues in 2012 on hoxd13a-overexpression.
In the Freitas et al. research, zebrafish was used to test the effect of the hoxd13a gene in the fin development stages. Additionally, the researchers introduced the hormone dexamethasone to induce hoxd13a over-expression and to examine its impact on the fold formation. Overexpression of the gene was associated with the development of an endoskeleton. The endoskeleton is responsible for limb formation. The article demonstrates the significant relationship between gene overexpression and formation of distal limbs. The analysis shows that previous studies have been consistent with the longstanding theories of fin to limb evolution. In fact, the researchers referred to other studies involving gene expressions of hoxa13b, cyp26b1, and pea3 that produced similar results to the hoxd13a overexpression (Scheider et al. 1121).
The findings show that a reverse evolution process can be carried out on fish embryos to demonstrate how fins developed into limbs. However, the article claims that the evidence from previous studies cannot be substantial without emphasizing on cell proliferation. The work of Freitas et al. is associated with noteworthy findings on limb evolution. In fact, the article lists evidences from the over-expression research, which promote all evolution principles presented in the transformation theories. The last section proposes the need for advanced research in shared gene components during the formation of fins and limbs. The researchers argue that the undiscovered regulatory circuits in the development of finfolds prevent paleontologists from gaining clear understanding of tetrapod evolution.
Conclusion
The article supports the tetrapod evolution theory, which maintains that limbs evolved from fish fins. The findings from the work of Freitas et al. demonstrate the significant relationship between the 5’Hoxd gene expression and the formation of limb digits. The evidence supports previous statements presented by paleontologists on the transformation of fish fins into limbs. In fact, it gives genetic evidence supporting the relationship between fin and limb formation.
Works Cited
Schneider, Igor, and Neil Shubin. “Making limbs from fins.” Developmental cell 23.6 (2012): 1121-1122. Print.