Monday, November 10, 2008
Sarah Palin vs. The Fruit Fly
By Shiban Ganju
Her mouth stretched with a condescending smile and her face reflected scorn. "You've heard about some of these pet projects, they really don't make a whole lot of sense and sometimes these dollars go to projects that have little or nothing to do with the public good. Things like fruit fly research in Paris, France. I kid you not." With this remark Sara Palin achieved a desirable target: she lost more votes.
Her defeat ensures a reprieve--probably temporary--from her contempt for research on other animals: worms, bacteria, fungi, fish, mice, rats, dogs, pigs, guinea pigs, baboons, monkeys, chimpanzees and many others. With their bodies--dead or alive--scientists have investigated physiology, developed drugs, designed instruments and evolved surgical procedures. The experimental use and abuse of these unwilling partners, especially of higher order animals and primates, has provoked ethical controversies, but the bacteria, fungi, worms and fish, have remained outside our ethical dilemma. These experimental organisms have yielded more fundamental knowledge because at genetic and molecular level some mechanisms stay unaltered in evolution from simple to complex organisms.
Fruit fly has hit the headlines but other lowly, yet equally interesting humble organisms - Caenorhabditis elegans (C elegans), Zebra fish, Escherichia coli (E coli) and many others deserve our gratitude. So much is already known about them because of years of work by thousands of investigators that it will be foolish to abandon them for political expedience.
What makes some organisms favorites for biologists?
Several techniques are in practice to study genes. One of them is to remove a gene or disable it partially or completely. The consequential defect in development defines the function of that gene. Another technique deciphers the DNA sequence and matches its sequence with a gene of a different animal or human. (Common ancestry in evolution has ensured similarity of genes or homologs in deferent species.) To draw any conclusion from these experiments requires animals with short life cycles. Investigators prefer those creatures for molecular and genomic research that develop fast, multiply rapidly and are inexpensive to maintain.
Fruit fly is Drosophila melanogaster - a 3mm long insect- that has been studied for a century, the longest period for any organism. Mutants for many of its 12000 genes are available and exposure to radiation and chemical can induce new mutations.It carries three pairs autosomal chromosomes and an X and Y chromosome. Its half-millimeter egg hatches into a larva, pupa and adult fertile insect in about 12 days. As the larva grows, the numbers of cells stay constant but increase in size to accommodate chromosomes, which divide hundreds of times but remain attached at the stands forming massive chromosomes. Small number of chromosomes, and their thickness at larva stage with light and dark bands make them accessible under a microscope.
Caenorhabditis elegans is a round worm, which lives independently in soil and feeds on bacteria and fungi. This multicellular, 1 mm long worm is transparent and is easy to maintain on a feed of E coli. It is a good model to study developmental, behavioral and neurobiology.
C elegans makes embryos in 12 hours and adults develop in 2.5 days. Total life span is over 2 weeks. It has 959 somatic cells and 302 neurons. Biologists have already mapped the development of all somatic cells and also traced all neural synapses, making it the only organism whose complete neural wiring is known, which makes it prime candidate for the study of neurobiology.
It has a relatively small genome and has 5 pairs of autosomal and 1 or 2 X chromosomes. Investigators have already mapped its 23,399 genes and have developed techniques their manipulation. 35% of its genes have human homologs.
Zebra fish or Danio rerio serves well in the study of vertebrate genetics. They grow from egg to larva in 3 days. The embryo is transparent and develops outside the mother, making it accessible for experiments. They can regenerate skin, heart, fins and even the brain in larval stage making them eminently exciting for the study of healing mechanisms after injury.
A pigmentation gene needed for melanin production in the fish has helped in comparative genomics to identify a similar gene in humans. One base pair difference in this gene differentiates European whites and African blacks.
Recently investigators in Children’s hospital in Boston have developed a new variant of this fish, which has a transparent body. This allows direct visualization of internal organs, production of blood cells and spread of cancer cells almost in real time in the live fish.
Escherichia coli is the workhorse in industrial microbiology. Insertion of an external gene into the Ecoli genome has laid the foundation of biotechnology. The technology helps production of therapeutic proteins. One of the first applications of this recombinant technique was the commercial production of insulin.
These are examples of some humble organisms among many that have improved human health. Scientists working on them deserve more support and not derision.
E coli and other poor organisms may be only four years away from Palin’s contempt, if the rumors of her presidential aspirations are true. She, the proponent of intelligent design, should be aware of another myth: the post election discourse among fruit flies.
What did one fruit fly say to the other? “If SP is creation of any design, surely it cannot be intelligent.”
Posted by Shiban Ganju at 04:47 PM | Permalink