3D Science

Thursday, February 10, 2005

Biology: The DNA Spiral

At the opposite end of the size scale from planetary bodies is the Microscopic world. Of particular interest is the DNA Spiral, a concept that leads itself admirably to 3D modelling.

The internet has heaps of resources on DNA and genetics, from basic information aimed at Primary School kids through High School and College texts to the professional level. Use these to understand the concepts behind what you are making.

Sometimes called the "Double Helix" this is also the name of the kids club of the Australian government science organisation, CSIRO, therefore it is only fitting that they have a DNA model available as a free paper model which is simple and colourful.

One beautiful example of papercraft is the DNA model available on the eyoshida website in Japanese. I have translated it using a translation engine, but it really needs someone with a knowledge of biology to review and edit the text into English.

Speaking of models, the Genetic Science Learning Center at The University of Utah has a "basics and Beyond" web site with a cumputer model of the DNA helix to build as well as an extensive Downloadable monograph on RNA using paper models to visualise the 3D structure which has an interesting section on modelling in science. I didn't know that James Watson and Francis Crick used a wire and cardboard model of the DNA double helix to discover and visualize the structure of DNA for the first time.

The DNAi Teacher Guide is another complete course that includes an "Origami DNA model". A novel and perhaps simpler approach.

Talking about paper models, I must bend my own rule, to mention a book for sale by Borin Van Loon entitled DNA: The Marvellous Molecule which seems to cover all this ground as well. With a double helix model, a nucleotide model, a baculovirus model to build to see how it injects its DNA into a parasitised cell, a 32 page minibook describing the material in accessible language and as an added bonus a storage box for the models. I haven't seen it but it sounds impressive. Borin Van Loon exhibited his work at the Whipple Museum in Cambridge, U.K. - next door to the famous Cavendish laboratories.

If you own some of the K'NEX ® brand constructors,there is a great tutorial on how to make K'NEX ® DNA Models. Aimed at High School or College, they take minutes to build & illustrate many important physical properties of DNA. More elaborate models can be built to illustrate complementary base pairing, transcription and replication.

This particular subject is often described as beautiful and many different media can be used to create models that reflect that beauty. From a simple model made using pipe cleaners, paper clips and Styrofoam blocks, to a yummy one made out of candy and even DNA jewelry made out of beads!

Access Excellence has two options for studying DNA in a "paper lab" (I like that description). With Discovering DNA Structure you make a model of the DNA spiral based on the four nucleatides that make up either side of the spiral ladder. The activity as it stands says to enlarge each nucleatide so that it fills a page (roughly 9" x 6.5") making a spiral 16" in diameter and a rung 6" high which means that a class could easily make a 14' floor to ceiling spiral! This material is the basis of an excellent treatment on the websites of the Montgomery County Public Schools, Stars and Seas and A/F Protein & Bio ID who (if I've read their profiles right) are based in Memorial University, St. John's, Newfoundland.

The other activity Cracking the code / Cloning Paper Plasmid takes you a step further. The bases of the DNA molecule are very much like the alphabet. The letters, in the alphabet, when written in a certain sequence, form a word and, likewise, the nucleic acids, when written in a certain sequence will write the code for the assembling of a specific protein. In the first half of the activity you learn to decode the DNA molecule, "read", and then "write" a message. In the second half you learn the four steps to clone the DNA molecule to make a vaccine.

The ENRICH website has a whole series of lesson plans available for downloading that cover DNA and genetics

Of course anyone who has watched CSI will know that DNA samples are invaluable in crime investigation, and these samples are prepared in a centrifuge. Looks cool! Did you know that you could build your own centrifuge from a kitchen blender and some simple and inexpensive extras? The plans for a do-It-yourself centrifuge are in the Amateur Scientist section of the January 1998 issue of Scientific American; by Carlson; 2 page(s). You can order the article or the whole issue online or you could check for the magazine at your local library.

Not everyone has the construction skills to make their own though. One option is the DiscoveryKids DNA Explorer that has a working centrifuge and electrophoresis chamber which will let you "extract clumps of real DNA from fruits and vegetables or solve 'crimes' by revealing DNA 'fingerprints'--telltale blue protein stripes in a gel mixture."

Looking a lot like the Nanoprobes that the Borg used in Star trek, Bacteriophages work in a surpisingly similar way. Bacteriophage means literally "bacteria eater" and that is what they do. Like the Borg nanoprobes they are tiny, a 'phage is roughly 20 nanometers in length, and they motor around under their own steam looking for an enemy to attack. In their case they are looking for bacteria which are ten times their size. When they find one they "land" on it and inject some of their genetic material which reproduces inside the host eventually consuming it and bursting forth in search of more prey!

Massamune Washington, an eminent three dimensional construction engineer, has a free model of a Bacteriophage on his website. Designed to be made from medium to heavy grade cardstock, was tested & built using 110lb (200g/m2) cardstock. This model has not been tested on standard bond paper which would almost certainly be to weak to hold the shape.


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