Noncoding DNA, also known as “junk DNA” describes portions of the DNA sequence that do not appear to have any presentable use — they do not encode for proteins, etc. In fact, in a most eukaryote cells, a rather large percentage of the total genome is noncoding DNA, but this varies between species. However, it is now a misnomer to call this material “junk,” because the more sophisticated we become at biochemistry, we find that many do have subtle biological functions, including the transcriptional and translational regulation of certain protein-coding sequences. Researchers also belive that other noncoding sequences have a likely, but unconfirmed function, as an inference from high levels of inherited tratis and natural selection processes (Masters, 2005, 163-5).
Researchers know that the amount of genomic DNA varies widely between organisms, as does the proportion of coding and non-coding DNA within these genomes. For instance, 98% of the human genome does not encode for protein sequences, but may still have vestigial uses. There are also a number of exceptions that may be the result of evolutionary processes that allowed for primitive organisms to even exist in the more hostile environment of early earth. For instance, an Amoeba dubia has 200 times the amount of DNA than humans; the puffer fish has a genome only about 1/8 the size of the human genome, yet has a comparable number of genes, but 90% of those are non-coding. Further, about 80% of human nucleotide bases may be transcribed, but transcription does not necessarily imply function (Pennisi, 2007).
Further, research shows that non-coding DNA may have an important biological function. Studies in comparative genomics reveals that some regions of noncoding DNA are considered to be highly conserved — sometimes millions of years — which implies that these regions are under strong evolutionary pressure for selection of positive traits. One interesting example is that of the genomes of humans and mice, which diverged from a common ancestor about 75 million years ago. Protein-coding DNA account for only about 20% of the conserved DNA, with the remaining majority appearing in noncoding regions (Ludwig, 2002).
Further, one of the key features of biological evolution is the conservation of energy. Why would an organism carry large amounts of unnecessary molecules that require energy if there was not a reason for their existence? Noncoding DNA must influence the behavior of other coding-DNA in ways not understood, or be the result of an evolutionary necessity. Recent studies have shown that, in fact, evolution has favored those species with large amounts of noncoding DNA because some of the “junk” actually form switches that do no encode proteins, but do regulate when and where genes are expressed (Carrol, 2008).
From and evolutionary standpoint, shared sequences of apparently non-functional DNA are a major line of evidence for the idea of common descent. For instance, the Hox genes are a set of transcription factors that specify segment identity — or whether a certain segment of the embryo will form the head, heart, abdomen, etc. It is sort of a digital body patterning, but the actual function of this gene shows tendencies as being highly conserved across long evolutionary distances. This can be demonstrated by showing that a fly can function quite well with a chicken HOX protein in place of its own. This essentially proves that, despite having lost a shared ancestor over 670 million years ago, a given Hox protein in chickens and flies are so similar that they can actually take each others place within the overall body system. Hox is so important (conserved because it lays out the basic format of an organism) that even a single mutation in the DNA of these genes has a drastic effect on the organism, proving these genes have changed relatively little over the last several million years (Gilbert, 2000).
Carrol, S.E. (2008). Regulating Evolution. Scientific American, 298(5), 60-7.
Chaisson, E. (2005, June). Early Cells. Retrieved October 2010, from Tufts University: http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/text/text_bio_1.html
Gilbert, S. (2000, July). Homeotic Selector Genes. Retrieved October 2010, from National Institute of Health: http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=dbio&part=A1971#A2009
Ludwig, M. (2002). Functional Evolution of NonCoding DNA. Current Opinion in Genetics and Development, 12(6), 634-39.
Masters, C. (2005). DNA and Your Body: What You Need to Know About Biotechnology. New South Wales: UNSW Press.
Pennisi, E. (2007). DNA Study Forces Rethink of What It Means to be a Gene. Science, 316(5831), 1556-7.
Walker and Jones. (2003). Genes and DNA. Sooke, BC: Kingfisher Press.
The Cambrian explosion is the first and only time in the fossil record that complex highly diverse organisms appear without much evidence of ancestral forms.
How do you explain this? In Origin of the Species, Darwin was a little unclear as to how he envisioned changes from one species into several. In some areas he spoke of a gradual change over a long period, but in his illustration, he implied that some species remained almost constant for a long time before a radical change. The debate has continued with two views being expressed as gradualism and punctuated evolution. Which view do you think has more data and why? In your answer, please refute the view that you think has the least evidence.
Charles Darwin was a British naturalist, most well-known for his Origin of Species, published when he was 50 years old. Originally intending to train for a medical education, Darwins interest in nature led him to neglect medicine and sign on as staff naturalist for a five-year scientific investigation on the HMS Beagle. Between his questions on the geological age and nature of the earth, coupled with his observations of the transmutation of species, particularly during the Beagles visit to South Americas Gallapagos Islands, he began to develop his theory of natural selection by 1838. A collegue of his, Alfred Russel Wallace, sent Darwin a manuscript early in 1858 that described a similar exploration of the theory of evolution, causing Darwin to agree to a joiont publication of the ideas at the Linnean Society in London. Darwin, of course, had written of the theory 15 years previous, but did not publish a book-length monograph until a year after the joint release (Darwin – A Lifes Work, 2006).
In science, evolution is one of the basic templates to understand the biology of an organism or ecological unit. It is the change in inherited traits of a population through a process called natural selection in which only the strongest traits are appropriately adapted to the environment, thus those traits from parents who live longer and are healthier are passed down to future generations. Evolution is the product of two opposing forces: variation in traits and mutation (Futuyma, Evolution). Darwins views convinced the scientific, and many others, that the world was not static. Instead, life is and has been continually evolving. One cannot imagine how much of a paradigm shift this was — it turned religion and philosophy around to the point that even in the 20th and 21st centuries the idea is considered so dangerous that it should be regulated in its dissemination, especially to children. Some see this explanation of life as the central organizing force that allows for complexity. Darwins natural selection is such a process that accounts for evolution to the point of both human minds and societies. Philosopher and cognitive scientist Daniel Dennett, in his 1995 book Darwins Dangerous Idea, says that:
Charles Darwins fundamental idea has inspired intense reactions ranging from ferocious condemnation to ecstatic allegiance, sometimes tantamount to religious zeal. Darwins theory has been abused and misrepresented by friend and foe alike. It has been misappropriated to lend scientific respectability to appalling political and social doctrines. It has been pilloried in caricature by opponents, some of whom would have it compete in our childrens schools with creation science, a pathetic hodgepodge of pious pseudo-science. Almost no one is indifferent to Darwin, and no one should be (Dennett, 2005, 17-18).
That other important scholars were influenced by Darwin is undeniable. To Sigmund Freud, for instance, Darwins basic premise was less natural selection, which Freud did not agree wholeheartedly, but more the biological notations of the process of evolution — gradual change over time. Indeed, the premise of Freuds work requires that there be an evolution of cognitive thinking, and certainly the development of the brain and function follows. Many of Freuds theories, in fact, were based not just on clinical work, but on “biological and neuro-physiological assumptions of the day” (Sulloway, 1992).
Darwinism has, for some, been a major cause in the reduction of religiousituy in the 20th and 21st centuries. While it is true that Darwinism rejects all supernatual causations of change over time, he remained a Christian. His theory explains the adaptedness and diversity of the world in a materialist manner, neither empracing or requiring an outside creator. This changed scientific inquiry and thoght by removing God from the scientific equation, and making room for scientific explanation of natural phenomena. This view, called positivism, produced a powerful revolution of itself that allowed.