Genetic Code, and What’s Cool About It

My father recently brought to my attention an article about a “second DNA code” discovered hiding within DNA:

DNA contains about 3 billion bases, more than 99 percent of which are the same in all human beings. “The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences,” according to the National Institutes of Health.

For instance, the genetic code uses a 64-letter alphabet called codons. The team found that some codons, which they refer to as duons, can have two meanings. One of the meanings relates to protein sequence, while the other relates to gene control.

Forbes and Geek.com both have good “easy there big fella” articles if you’re interested in why this isn’t necessarily news, but this is a great opportunity to talk about what we do know about DNA and what you as a probably-not-genetics-researcher should know. I’m going to assume you’ve at least heard of DNA, but not much more.

Every cell in your body typically has 23chromosomes. Each of these chromosomes is made of a lot of DNA (each strand is between 2 and 3 meters long), coiled up in some pretty crazy ways, but at the most basic level, you’re looking at that classic “double helix” coil. Each strand of DNA has a bunch of genes on it with a bunch of stuff in between – think of it like a really long book with some chapters in English and some in Finnish. You page through it looking for English words; when you see some, you start reading, and you get some ideas out of it.

The English chapters are the protein-coding genes, which use the 64-codon alphabet the quote above is talking about. Some of the Finnish chapters, on the other hand, are actually functioning to determine how frequently you read a particular English chapter. These are transcription factors.

Here, of course, is where my analogy breaks down; a protein binds to the transcription factor site and says HEY RNA POLYMERASE COME READ THIS ONE, and the RNA polymerase comes over and makes a protein out of the gene the protein was yelling about. If the protein made is another one that can bind to another transcription factor site, you can get positive feedback loops, and you get more and more of a certain kind of protein (until there’s “enough”, and you start getting other proteins that bind and say NOPE NO GENE HERE I DON’T KNOW WHAT YOU’RE TALKING ABOUT, and then that protein’s levels go down for a while).

So: chromosomes are made of DNA, DNA has genes and other stuff, that other stuff can be used, among other things, to tell the cell which genes to read and how often. DNA isn’t just a recipe book, it’s a meal plan and timer.

The research I’m doing, which is related, has to do with the fact that sometimes the same gene can make a bunch of different proteins, because sometimes the cell decides it doesn’t really like a particular part of a gene today, so it throws part of it away. That means you’re missing some codons (that 64-letter alphabet again), and so the resulting protein is actually measurably different. Which is AWESOME.

5 thoughts on “Genetic Code, and What’s Cool About It

  1. MichaelF says:

    Wow…very, very cool. While having only the most basic lay person/non-scientist understanding, I’m still amazed that knowledgeable people are making discoveries like this, which increases and broadens everyone’s understanding. Not knowing doesn’t mean not appreciating.
    Same with physics — recently saw an article in the popular (as opposed to scholar/peer reviewed) science press suggesting that recent mathematical proofs confirm some conjectures in string theory…which, according to the article, means the known universe might only be a 3 dimensional hologram (oh, and if only I had a little weed and an idle week to contemplate, hahaha)…
    But, frivolity aside, pursuit of knowledge, whether for practical use or for its own sake is always a good idea and even better investment. Many years ago I read a quote from (I think) physicist Enrico Fermi — asked what theoretical/pure science (as opposed to practical science) did to aid the national defense, he replied, “it gives us something worth defending.”
    Yes.

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  2. pansypoo says:

    i have always been drawn to the mistakes. old medical books of baA. my mom was getting a med degree when i was a kid + i’d look at the pictures of XXX, XYY + others. now i have an old oral pathology book retrieved from a dumpster. oh hey! ann coulter!

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  3. Hank says:

    And to extend your analogy, the duon thing says that sometimes a chapter you’re reading in English can also be read in Finnish.

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  4. Hobbes says:

    Hank – more that there are footnotes in Finnish, but yes, that’s the basic idea. The duon idea comes from the idea that there are multiple codons that code for the same amino acid, so the benefit of using one codon in a particular place over another equivalent codon is to give the cell further information for transcription factor binding.
    The postdoc in my lab is doing some work on this, which looks at the actual physical shape of the DNA strand and how that’s affected by which nucleotides are in the gene (A/T and C/G all have slightly different shapes, which can combine to make it easier or more difficult for a transcription factor to bind).

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  5. Lex says:

    23 chromosomes? I thought it was 46 (23 pairs).

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