innovative approach to teaching the morphology of viruses: the use of models

ABSTRACT

To develop a general inters about viruses, to understand the complex structures of the viruses in a simple way, to get an idea of the three dimensional picture of the viruses and to classify the viruses in a way so that it is easier to remember the viruses. Virus is a living chemical made up of nucleic acids covered by protein coats and in some viruses further covered by lipid envelopes. Basically the function of the protein coat is to protecte the nucleic acid. If this protein coat is absent this is called VIROID while the name PRION is given to something in which presence of only protein is documented. Viruses have three types of structures. Helical symmetry You can use a ball and fill it with a wire. Cubic symmetry is based on icosahederon and is further studied by vague electron micrographs. Our effort here is to simplify the details of this structure in the form of a model. The icosahedrons are described with 12 vortices [corners] and 20 surfaces. The subunits [capsomeres] of the capsid [protein coat] described in the books are either calculated by mathematical formulae and every thing is left to the imagination of the learner. Here we have tried to describe the same thing by simple logic and simple calculation by using self prepared models. The identification of the viruses using the electron microscope is based on the details of the number of these capsomeres and the arrangement of these capsomeres present in this virus coat. Soccer Ball like structure and Picrona virus. There are 12 red colored polygonal pieces, one on each of the vortices. There are 20 blue colored hexagonal pieces [one on each of the total of 20 surfaces] giving it a soccer ball like appearance. Viruses included in this group i.e. Picorna viruses include the Entero virus [Polio virus, Coxsackie, ECHO and entero virus] and the Rhino virus. The core of the Hepatitis B viruses also has the same looks. Adeno Group of Virus. There are 12 red colored pieces [one on each vortices]. There are six blue colored capsomeres on each of the 20 surfaces [6 multiplied by 20 = 120 surface pieces] There are four white colored capsomere on each of the 30 edges [4 multiplied by 30- 120 edge pieces]. There are a total of 252 pieces in Adeno group of virus. Models of DNA viruses can also be made by using plastic material like old X ray plates. Plastic balls may be used or bottom of the plastic bottles can be used to give the round shape in preparing models of RNA Viruses. An old Chinese saying. If you read, you are likely to forget. If you see you will understand. If you do it yourself you will remember it