Practice question

The physical nature of viruses was a mystery until 'W.M. Stanley' in 1935 biochemically manipulated them. The NCERT textbook highlights his discovery that viruses could actually be 'crystallised', and these biological crystals consisted almost entirely of tightly packed proteins. This proved they were inert outside a host, cementing their status as non-cellular obligate parasites lying on the boundary of living and non-living.