TOM RUTKOWSKI, Ph.D.
assistant professor
University of Iowa

Marilyn, Versailles, Ohio, USA

I am doing a project for my biology class in which I have to create a 3-D model. The model can be anything, as long as it is related to biology somehow. I was wondering if you could help me out with what I should do. There are so many options for me out there, but they all seem to be too difficult. Do you have any recommendations on what I should build a 3-D model of? Please help. I don't want it to be too complicated, though, as my sculpting ability is very limited.

Tom Rutkowski
assistant professor,
Department of Anatomy and Cell Biology,
University of Iowa
(former HHMI postdoctoral fellow)

Sounds like an interesting project. One general principle of biology is that form reflects function. Put another way, the shapes of biological structures are closely related to their specific roles. This is true from the shapes of organs like the heart and kidney all the way down to individual macromolecules. Therefore, I think the best model you can make is one that will yield information about the function of whatever you're modeling.

Remember that you can model biological structures at several levels of complexity. You could make a model of

• an organ, like the heart or lung;
• a cell, like a skin cell, red blood cell, or neuron;
• an organelle within the cell, like the endoplasmic reticulum or a ribosome; or
• individual macromolecules, like proteins or nucleic acids, which, though very small, have unique and distinctive structures.

I'm not sure about exactly how your teacher will be evaluating your project (you should check!), but I would say that if your sculpting skills are limited, you may want to make a model that's more schematic than accurate down to the last detail. Let's say, for instance, that you chose to model the heart.

Rather than using a lump of clay to construct a sculpture that looks like the outside of the heart, you could make a cut-open model, where you could show the inside of the heart, complete with chambers, valves, blood vessels, etc. You could use straws to make your valves and blood vessels, and other simple materials to make the actual chambers. It's more important to show how the blood flows (that is, its path from the time it enters the heart to the time it leaves) than what the heart actually looks like.

The structure you choose to model should depend on what interests you. The brain? The eye? DNA? I suggest you search the Internet or textbooks for pictures of biological structures that intrigue you. Whatever you choose, be sure to make the important functional features obvious in your model. For instance, if you opt to make a model of DNA, you'll want to make each base, A, G, C, and T, a different color so it's clear that A always pairs with T and G always with C in the DNA double helix.

An unusual approach that would be very interesting would be to build the translating ribosome. The ribosome, as you may know, is the cellular machine that translates messenger RNA into protein. Although we know the gross structure of ribosomes and that they're each composed of numerous proteins and several small bits of nucleic acid, the precise arrangement of these components is not known. Key elements in your model would be the large and small subunits of the ribosome (could probably be made from clay or something similar), the mRNA (could be made from a simple rod), the emerging polypeptide (could be represented by beads on a string), and the two tRNAs associated with the ribosome, one containing the incoming amino acid and the other linked to the growing protein chain. The important functional feature of the ribosome is its ability to both move along the mRNA and transfer the growing polypeptide from one tRNA to another. Your model would demonstrate to your class how this is accomplished.

Although some of your classmates may choose to build a heart, I would guess that none would model the ribosome, and your model could be very informative and unique.

For a real-time view of a virtual heart pumping away, visit "The Visible Heart" at http://www.hhmi.org/grants/lectures/multimedia/ .

For more information on how ribosomes work, as well as some pictures of ribosomes in action, consult http://cellbio.utmb.edu/cellbio/ribosome.htm .

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