Question

According the Caspar and Klug theory, circle which of the following would be allowable values for the number of subunits in an icosahedral (or ‘spherical’) viral capsid? Explain you answer

30 60 120 180 240 300 360 420 540

Answer 1

Following would be allowable values for the number of subunits in an icosahedral (or ‘spherical’) viral capsid:

T=1; 1 x 60 = 60

T=3; 3 x 60 = 180

T=4; 4 x 60 = 240

T=7; 7 x 60 = 420

T=9; 9 x 60 = 540

This is because according the Caspar and Klug theory, only spherical icosahedral viruses with 1 x 60, 3 x 60, 4 x 60, 7 x 60, 9 x 60, etc. identical subunits should occur, but that e.g. 2 x 60 and 5 x 60 would not occur where 1,3,4,7 and 9 are the triangulation numbers (T).