The Biggest Piece Of DNA Ever Made 70
An anonymous reader writes "Forbes has a story on 'the biggest piece of artificial DNA ever made'. The real story is that companies are racing to produce longer and longer DNA fragments to serve the growing science of synthetic biology." From the article: "On a piece of DNA as long as the one made for Microbia, ten or more genes may be present. By studying more than one gene at once, researchers hope to get a better picture of how they work in concert to produce an organism. Another advantage: These stretches can also be made to contain all the DNA letters that occur between genes. Scientists once thought of that stuff as junk, but many now believe it may regulate how the genes work or provide some other function."
exons/introns (Score:5, Informative)
To clarify: a stretch of DNA that actually gets turned into RNA and thence into proteins is an exon, and the DNA that lives between exons is called an intron. It's been known for a long time that there are sequences before an exon that control it: regulators, promotors, and repressors, that are activated or deactivated by proteins binding to them during DNA reading, and in some cases there are sections of DNA that are processed into RNA, that help stabilize the RNA and are then clipped out before the RNA becomes protein, so they also have a function. (This is part of the reason that making insulin artificially has been tricky: you can't just stick the DNA into a bacterium and have it crank out insulin because the DNA is in a couple sections and requires post-processing.)
Also, many of the introns contain echoes of old sequences that used to be useful way back when, and aren't anymore, or bits of viruses that integrated into the genome hundreds or thousands of generations ago and are now widely spread in the population, and some intron bits are designed to facilitate shuffling of chunks of DNA into different orders for proteins that come in a wide variety of flavors with the same start and end sequences. Antibodies, for instance, have long, consistent, identical start and end chunks with wildly variable center chunks. (Think of a key, with differing teeth to fit various locks, but the same end piece, to fit your hand. Likewise an antibody has a hypervariable section that, for each antibody, can adhere to precisely one antigen, and a nonvariable section that signals passing cells that it has/hasn't found any of that antigen.)
Getting to go play around and make any set of repressor/promoter sequences and change the distances between them is a really nice tool, and being able to make massive sequences like this, helps play with gene interactions and with massive proteins like antibodies. Think of this as the beginnings of the transition from transistors to integrated chips, or maybe it'd be more apt to say from single computers to the beginnings of networks.
Re:"junk" DNA (Score:3, Informative)
However odd it may be, human males have the ability to breastfeed, though since pregnancy is impossible, most people do not realize it. Granted, I am not sure the feasability or usefulness, but it is physiologically possible in certain cases.
http://en.wikipedia.org/wiki/Male_lactation [wikipedia.org] for a start to your research, and the end of mine.
Re:exons/introns (Score:3, Informative)
Anyway, your description might lead people to assume that most of the DNA present in a human that's not an exon would be an intron or a sequence of direct regulatory use. That's obviously not the case, or at least the regulatory effect is very limited in, for example, extremely long repeats and other sections devoid of transcriptional activity. If those have any other effect than "just" modifying the chemical environment slightly by their sheer presence, that's a great unknown to us right now.
not as big (Score:2, Informative)
http://www.bathsheba.com/crystal/dna/big.html [bathsheba.com]
If that's too big for you, they also have:
http://www.bathsheba.com/crystal/dna/ [bathsheba.com]