Ultraconserved DNA Elements - An Evolutionary Enigma
Ultraconserved DNA elements are short chunks of genomic sequence 200 bases or more that are highly similar (conserved) among different types of animals and are generally noncoding (1,2). Hence, they should have very little evolutionary selective pressure acting upon them and evolve rapidly (3).
Rapid evolution in DNA is thought to be represented by shared sequence that are similar at some level, but variable between groups of organisms. The more variable or different the sequence is, the more evolved it is thought to be. In general, areas that contain more critical information in the genome, such as gene-rich areas, are thought to evolve more slowly because they tolerate less mutation and are more heavily selected (subject to the pressures of natural selection (3).
The enigma or paradox with ultraconserved DNA elements is that they appear to have minimal functionality, yet they remain unchanged across diverse groups of animals. According to the standard model of evolution, however, they should be highly variable since selective pressures have little influence upon - they should be free to mutate. A quote is posted below from an evolutionary research paper stating this issue.
“Most ultraconserved elements are noncoding and have been evolutionarily conserved since mammal and bird ancestors diverged over 300 million years ago. The reason for this extreme conservation remains a mystery.”(4)
This enigma is typical of the mosaic observed across the spectrum of life. In cases where organisms have similar nutritional needs, physiologies, body plans, and other shared traits, gene sequences for these traits will often be similar at some level. However, separate types of animals also have DNA sequences and patterns that are unique to that particular organism - these are the types of sequences that defy man’s ideas about evolutionary hierarchies and hypothetical selective processes.
Remarkably, the only historically predictive idea that accurately accounts for these types of patterns in life is the text in the book of Genesis in the Bible that specifically states that separate created kinds were made with their own reproductively defined gene pools. Exactly what we observe in modern biology research.
- Bejerano, G, et al. 2004. Ultraconserved Elements in the Human Genome. Science Vol. 304 no. 5675 pp. 1321-1325
- Ishibashi, M, et al. T.2012. Evolutionary growth process of highly conserved sequences in vertebrate genomes. Gene. 504(1):1-5.
- Chen, C.T., J.C. Wang, and B.A. Cohen. 2007. The Strength of Selection on Ultraconserved Elements in the Human Genome. Am J Hum Genet. 80(4): 692–704.
- Katzman, S. et al. 2007. Human Genome Ultraconserved Elements Are Ultraselected. Science Vol. 317 no. 5840 p. 915