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Genetic Linkage

Ricki’s Rant: Genome Sequence, NOT Genetic Code

Strawberries can use a gene from peanuts to withstand frost because the genetic code is universal.
Humans do not have their own genetic code, and certainly each of us does not have his or her own. The idea of our utter uniqueness might be attractive, but genetics just doesn’t work that way. And it’s a good thing.

The genetic code is the correspondence between a unit of DNA information and a unit of protein information. The code was “cracked” in the 1960s, not in 2000 when the human genome was sequenced.

The ubiquity of “computer code” has accelerated the misuse of “genetic code” to mean a string of DNA letters, but genetic code is more like Morse code: it is the correspondence. CCC encodes proline in a person, an alligator, or a fern. It isn’t proline in Barack and alanine in Michelle.

Two recent gaffs from prestigious places:

The Wall Street Journal, January 10: "Soon, $1,000 Will Map Your Genes." I could read no farther than "the human genetic code" and, even worse, "a person’s genetic code."

National Geographic, January cover story on twins: “Because identical twins come from a single fertilized egg that splits in two, they share virtually the same genetic code.” Well, yes, but so do aardvarks and slime molds and gingko trees and bacteria and the not-even-alive viruses.

Using “genetic code” and “genome sequence” synonymously might seem a mere matter of semantics, but it isn’t, for it is the “universality” of the genetic code that lies behind much of biotechnology.

If the genetic code was not universal, then:

•Bacteria couldn’t manufacture biologic drugs, such as human insulin.
•Genetically-modified crops could not produce insecticide.
•A virus couldn’t deliver gene therapy.
•Model organisms such as mice, zebrafish, worms and flies couldn’t harbor human genes, enabling us to investigate disease and develop drugs.

It’s logic. How could two human beings ever be able to produce a child, if the same DNA sequence meant different things in different people?

Individuals have different DNA sequences. Different genomes. Different collections of gene variants, and different gene variants. That’s what makes life interesting. But the CODE is the same. It has to be, or we wouldn’t have life. The X-Files actually got this right when Dana Scully happened upon an extraterrestrial life form that had a 5-base genetic code, rather than our earthly 4-base one.

I will continue to stop reading articles as soon as I see misuse of “genetic code,” continue to explain in my textbooks why we don’t have individual genetic codes, and I will continue to use pieces of the genetic code as my passwords. Combined with the year that Watson and Crick discovered DNA's structure, they make great alphanumerics.
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