Molecular biologist Francis H. C. Crick and zoologist James D. Watson discovered the double-helix structure of DNA in 1953, a discovery that opened the doors to the study of genetics. Crick, after a long struggle with colon cancer, died at a hospital in San Diego on July 28, 2004. He was 88 years old. A 1962 Nobel prize was awarded to them for their discovery.
Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints or a recipe, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.
Chemically, DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription.
Within cells, DNA is organized into structures called chromosomes. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms (animals, plants, fungi, and protists) store their DNA inside the cell nucleus, while in prokaryotes (bacteria and archae) it is found in the cell's cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed. This discovery led to the Human Genome Project and many research efforts related to it. Online sources describe the HGP:
“Completed” in 2003, the Human Genome Project (HGP) was a 13-year project coordinated by the U.S. Department of Energy and the National Institutes of Health. During the early years of the HGP, the Wellcome Trust (U.K.) became a major partner; additional contributions came from other nations. See the history page at http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml for more information.
Project goals were to
1.identify all the approximately 20,000-25,000 genes in human DNA,
2.determine the sequences of the 3 billion chemical base pairs that make up human DNA,
3.store this information in databases,
4.improve tools for data analysis,
5.transfer related technologies to the private sector, and
6.address the ethical, legal, and social issues (ELSI) that may arise from the project.
“Though the HGP is finished”, analyses of the data will continue for many years. Follow this ongoing research on the Milestones page at http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml. An important feature of the HGP project was the federal government's long-standing dedication to the transfer of technology to the private sector. By licensing technologies to private companies and awarding grants for innovative research, the project catalyzed the multibillion-dollar U.S. biotechnology industry and fostered the development of new medical applications.
There are multiple definitions of the "complete sequence of the human genome". According to some of these definitions, the genome has already been completely sequenced, and according to other definitions, the genome has yet to be completely sequenced. There have been multiple popular press articles reporting that the genome was "complete." The genome has been completely sequenced using only the definition employed by the International Human Genome Project. A graphical history of the human genome project shows that most of the human genome was complete by the end of 2003. However, there are a number of regions of the human genome that can be considered unfinished:
First, the central regions of each chromosome, known as centromeres, are highly repetitive DNA sequences that are difficult to sequence using current technology. The centromeres are millions (possibly tens of millions) of base pairs long, and for the most part these are entirely un-sequenced.
Second, the ends of the chromosomes, called telomeres, are also highly repetitive, and for most of the 46 chromosome ends these too are incomplete. It is not known how much sequence remains before the telomeres of each chromosome are reached, but as with the centromeres, current technological restraints are prohibitive.
Third, there are several loci in each individual's genome that contain members of multigene families that are difficult to disentangle with shotgun sequencing methods - these multigene families often encode proteins important for immune functions.
Other than these regions, there remain a few dozen gaps scattered around the genome, some of them rather large, but there is hope that all these will be closed in the next few years.
In summary: the best estimates of total genome size indicate that some 90% of the genome has been completed and it is likely that the centromeres and telomeres will remain un-sequenced until new technology is developed that facilitates their sequencing. Most of the remaining DNA is highly repetitive and “unlikely to contain genes”, but it cannot be truly known until it is entirely sequenced. Understanding the functions of all the genes and their regulation is far from complete. The roles of junk DNA, the evolution of the genome, the differences between individuals, and many other questions are still the subject of intense interest by laboratories all over the world.
Crick wrote:
"The age of the earth is now established beyond any reasonable doubt as very great, yet in the United States millions of Fundamentalists still stoutly defend the naive view that it is relatively short, an opinion deduced from reading the Christian Bible too literally. They also usually deny that animals and plants have evolved and changed radically over such long periods, although this is equally well established. This gives one little confidence that what they have to say about the process of natural selection is likely to be unbiased, since their views are predetermined by a slavish adherence to religious dogmas."
He also lectured (#18):
"Svante Arrhenius in 1908 proposed the "panspermia theory" - that life originated on Earth with the arrival of spores that had drifted through space from some other planetary or solar system. Among those who favor this hypothesis, Francis Crick argues that the overwhelming biochemical and molecular evidence suggests that the last common ancestor was already on earth 3.5 to 3.6 billion years ago when the history of life began on earth. "
Is the Panspermia idea a viable one? The possibility that life once existed on Mars made news recently. The evidence is questionable but still a possibility. Is it likely that microbial life came to earth from Mars or some more distant extraterrestrial source? "Deinococcus radiodurans, a bacterium highly resistant to radiation, would be a good vector for panspermia, said Dr. [Kenneth W.] Minton [of the Uniformed Services University of Health Sciences in Bethesda, MD]. While drifting through interstellar space for many thousands of years, it might acquire a shell of interstellar crud that could protect it [from the intense heat generated] when it entered some planet’s atmosphere space".
A pastor preaching on KSIV radio just this week postulates that this means Crick recognized that the DNA double helix protein strands are simply too complex for life to originate by Darwinian means. Therefore, they must have come from extra-terrestrial means.
Make no mistake about it, Crick referred to himself as a skeptic and an agnostic with "a strong inclination towards atheism”. But even casual comments can make huge impacts on thinking and bruise the evolutionary thinking of the Darwinian cult. It is likely that a small movement emanating from the evolution-medical research field has, or will move out from the Darwinian survival of the fittest, and life originating from inanimate materials into the “panspermia” theory of origins. One cult can generate still another.
Compare this with another faith:
By faith we understand that the worlds were prepared by the Word of God, so that what is seen was not made out of things which are visible… And without faith it is impossible to please Him, for he who comes to God must believe that He Is and that He is a rewarder of those who seek Him.
Labels: Origin of the Species
