On Genomes, Stem Cells and Cloning
Many can recall the double helix adventure of research fellow James Watson and graduate student Francis Crick in 1953 at Cambridge University. However, the notion of nucleic acid was discussed as early as 1872 at the University of Basel by Friederich Miescher. In 1943, an American, Oswald Avery, proved that DNA carried genetic information. In the late 40’s and early 50’s, people like Linus Pauling and Erwin Chargaff provided the foundation for the helix and nitrogen base pairs, and Rosalind Franklin of King’s College in London first “saw” the coil in x-ray diffraction images of DNA. Maurice Wilkins, also of Kings College, “leaked” this information to Watson and Crick, and all three went on to win the Nobel Prize in 1962. Franklin had passed away by then.
One can only wonder how Watson, who was once more interested in birds, and Crick, who designed naval mines in World War II, both with little training in microbiology, went on to become Nobel Laureates discovering what has been lauded as the most important piece of biological work this past century, if not ever. So, my adventures into crime, war and religion might still, in time, be justified.
Watson in 1988 became the first head of the National Institutes of Health Office of Human Genome Research, which, with the U.S. Department of Energy, initiated the Human Genome Project (HGP) in 1990. 1992 was a tumultuous year, as James Watson resigned and J. Craig Venter also left the NIH. Venter formed Celera in 1998 and said that he would sequence the human genome in three years at a cost of $300 million. After a series of collaborations and squabbles between the federal and private competitors, they split at the end, only to both publish their successful findings: HGP in Nature (February 15) and Celera in Science (February 16).
A gene, a DNA sequence containing the template for the synthesis of a protein or RNA product, is the unit of heredity in living organisms. A genome is the set of genetic material of an organism. The human (homo sapiens) genome is composed of 24 chromosomes with approximately 3 billion DNA base pairs containing as few as 20,000 genes (but as much as 25,000), a number which has been revised down from the initial 100,000 prediction. A mouse has about the same number of genes, of which 99% or so are similar.
All living things have cells—as reported earlier, approximately 10 trillion in a human—with the primary genetic materials being deoxyribonucleic acid (DNA) and its partner, ribonucleic acid (RNA). DNA is always a double stranded coil and RNA is single stranded. There are only four components to DNA: adenine, cytosine, guanine and thymine. Thus, while we have 26 letters in our alphabet, DNA has only four: A, C, G and T. These four letters are combined in three-letter words to produce 20 amino acids, which are sequenced to make proteins. Life could have been a lot more complicated.
Why are we so like rodents? Evolution indicates that we split off from them only 75 million years ago, and this is but a flash of time in the realm of genetic mutation. Interestingly enough, the mouse DNA actually has shown a higher order of hybridization, but mostly because they have a shorter lifetime. Another way of looking at this in the extreme is that we need 5 million years to pass through 300,000 generations. Bacteria require only 25 years. Thus, germs mutate quickly away from current treatments and can more easily adapt to changes in the environment if, say, global warming becomes the Venus Syndrome.
Of these couple hundred different genes, rodents have developed a few to give them a better sense of smell. The whole basis of evolution is that our DNA now and then makes a mistake and the product turns out different—usually worse, but sometimes better—adapting to the changing environment. This is called evolution.
We are genetically closer to the apes, as there is about a 98.77% (or 99.2%, depending on time and report) similarity pattern between humans and our earlier ancestors from which we diverged 6 million years ago. We actually have one less chromosome than these primates, as it appears that our chromosome 2 represents a fusion of two mid-sized ape chromosomes.
Here it gets a bit complicated, but if DNA insertions and deletions are taken into account, we only share 96% that of chimps. A comparison shows these genetic differences:
o 60 times less between human and chimpanzee than between
human and mouse
o 10 times less between human and chimpanzee than between
mouse and rat
o 10 times more between human and chimpanzee than between
human and human
In a nutshell, some might be comforted that we are, indeed, more like a monkey than a rat. Book 1 talked about our common ancestor from Africa who lived about 3.2 million years ago, Lucy, named from a Beatles song, Lucy in the Sky with Diamonds, which was playing on the radio when Donald Johanson and his team were celebrating the find. Chapter 5 on religion will glance at Adam and Eve, say, 6000 years ago, but here we’ll go back much further in time, to find Luca.
-
The Dow Jones Industrials jumped 115 to 9286, while world markets, while, except for Japan, major world markets all increased. Ford is surging, as the Senate sets to add $2 billion for the cash for clunkers program. Crude oil jumped into the seventies per barrel and gold went up $3/toz to $957.
-
Lana, now at 30 MPH has passed way south of Kauai and continues west. However, three more disturbances have just formed in the East Pacific. All three now equal or exceed Lana in intensity, but as they keep moving west northwest and leave the hot spot, they should all eventually weaken. Two storms also just formed in the West Pacific. See below.
-
No comments:
Post a Comment