Darwin Awards 4: Intelligent Design by Northcutt Wendy

Author:Northcutt, Wendy [Northcutt, Wendy]
Language: eng
Format: epub
Published: 0101-01-01T00:00:00+00:00

However they arose, the viral vector is here to stay. They all have the same grisly modus operandi. First, the dastardly buggers break through the cell wall. Some pick the lock of an existing portal and sneak past the molecular doorman disgUised as legitimate cargo. Others are constructed like an off shore drilling platform. They land on jointed legs, drop a drill bit onto the exterior of their target, and then begin boring in for all they're worth.

Once the membrane is breached by whatever means, viruses inject a packet of trouble into the interior, which makes for the nucleus and commandeers the genetic machinery to make more viruses. The end result is a person who sickens, and sometimes dies.

But there is a consolation prize. Geneticists have found that this viral scourge is incredibly useful in shedding light on all manner of mysteries biological.

Viruses Are Our Friends, Part 1

Some of these little influenza bugs are retrovimses like HIV and feline leukemia. retrovirus (n): genes carried on single-stranded RNA, which co-opts the nucleus of the infected cell to convert itself into DNA. This DNA sometimes inserts itself into the cell's chromosomal DNA.

These viruses are RNA, and typically "reverse-transcribe" their RNA into DNA for integration into the host's genome. When that happens, they snip the DNA and insert themselves surreptitiously into the host's chromosome, where they lie dormant, sometimes for years, before activating. Later, they activate and begin making more RNA, which in tum inserts itself into the genome, until the entire cell basically falls apart. Then the RNA retroviruses are off to seek new, healthy cells for more viral adventures.

But if the retrovirus doesn't reactivate, this life cycle fails. While the infection is contained, the cell is left with inert viral sequences scattered throughout its genome. They can cause problems. The inert sequences may disrupt a key gene, for example, and uncontrolled replication may ensue-the beginning of cancer. Or it could spark an autoimmune disorder like multiple sclerosis, or exotic forms of painful, debilitating inflammatory disease. But often the retrovirus simply sits in the chromosome, inert and disregarded.

Now consider inheritance. Sometimes, by a stroke of fate, the infected host is a sperm or egg cell, which becomes a child. That child has those inert viral sequences in every single cell of his body. If those sequences happen to lie near an allele (one member of a pair of genes) that becomes ubiquitous in the population through natural selection, then all members of the species will carry the same genetic "signature" in every cell of their body. These ghosts of infections past are called endogenol1s retrovimses, or more affectionately, ERVs.

An ERV found in the same DNA location in two people provides powerful evidence, admissible in court, that they share a common ancestor. All humans share many ERVs in identical locations, which is no surprise. We all have common ancestors if one looks far enough back. But here's where it gets interesting: Chimps and humans also have ERVs in common. If identical ERVs serve

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