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May 21, 2010

A Brief History of Unnatural Selection

http://www.jewishjournal.com/blog/item/a_brief_history_of_unnatural_selection_20100521/

Indulge me as I digress from writing about health this week to write about an important scientific breakthrough.

People have been altering the living things around us as long as we have been around.  We domesticated wild wolves into tame dogs and kept them for protection and as pets.  Eventually humans began to farm, and raise livestock.  We then began selecting the best animals to breed for the next generation, and we selected seeds from the best plants to sow.  Generation after generation, we changed the animals and plants that we had domesticated by allowing only those with characteristics we valued to reproduce.  We had no idea what made wheat grain larger or why some sheep grew more wool, we just knew that these traits are inherited, and by breeding the right specimens we could get more of what we wanted.  Through this simple repetitive selective breeding all human crops and domesticated livestock eventually became unrecognizable from their wild origins.  The wheat we eat today has about as much resemblance to pre-human wheat as my neighbor’s yippy dachshund has to a wolf.

So millennia before any people were rigorously studying living things (engaged in what we now call biology) people were progressively modifying many animal and plant species.  In 1859 Charles Darwin published “On the Origin of Species” his landmark work which argued that just as people select the pet cats and tomatoes and carrots that form the next generation, nature selects the survivors of every species to reproduce.  He proposed that it is this selection by nature (i.e. natural selection) that explains how all species change over time and how new species arise from older forms.

At about the same time Gregor Mendel showed that inheritance follows certain predictable patterns.  The offspring are not simply a blend of the traits of the parents.  Rather the parents’ traits are somehow transmitted in distinct indivisible packages (now called genes) which are inherited and expressed according to simple rules he described.

In the 1940s and 50s the molecule carrying genetic information was found to be deoxyribonucleic acid, DNA.  And in 1953 James Watson and Francis Crick discovered the shape of the DNA molecule – the double spiral staircase – that allowed it to serve as a molecular information storehouse.

Since then the fields of molecular biology and genetic engineering have exploded, with the development of techniques to identify, isolate and sequence genes.  In 1977 the entire set of genes (genome) of a virus was sequenced, meaning its entire DNA code was deduced.  Since then the genomes of many species, including humans, have been sequenced.  Genes have been inserted into crops to make them more resistant to disease and the molecular mechanisms of some genetic diseases have been discovered.

(By the way, those who object to genetically modified organisms in their food should not eat any crops at all since all modern crops have been modified through human selection since prehistory.  Genetic modification is just a finer tool for continuing the work of millennia.  Now that I think about it, these critics should also only keep wild tigers and wolves for pets.)

This week another threshold has been crossed.  Investigators synthesized an entire genome from scratch, inserted it into cells that had their original DNA removed, and formed cells that reproduced and expressed their new synthetic genes.  The effort took 15 years.  The achievement has no immediate practical uses.  It was simply a demonstration of the technologies required for such a feat.  Potential practical uses are myriad, but are likely far off in the future.  Their discovery was published in the journal Science and has received much press attention.

Though we have much more to learn, the pace of discovery is accelerating.

Learn more:

Wall Street Journal article:  Scientists Create Synthetic Organism

Science article:  Creation of a Bacterial Cell Controlled by a Chemically Synthesized Genome

The Ancestor’s Tale by Richard Dawkins is a fascinating tour through the history of life on Earth.

Important legal mumbo jumbo:
Anything you read on the web should be used to supplement, not replace, your doctor’s advice.  Anything that I write is no exception.  I’m a doctor, but I’m not your doctor despite the fact that you read or comment on my posts.  Leaving a comment on a post is a wonderful way to enter into a discussion with other readers, but I will not respond to comments (just because of time constraints).

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