Some glycoprotein structures emerge from the lipid coat. Some viruses have haemagglutining spikes HA which stick to the surface of red blood cells causing clumping of blood. The envelope is essential for the infection process. Treatment with detergents or organic solvents such as chloroform or ether damages the lipoprotein layer and inactivates the virus. They have a central nucleoid core of DNA covered by a lipoprotein membrane with spikes.
Phages Are virus particles with a head of icosahedral symmetry and a tail of helical symmetry.
Examples of phages are the T2, T4 and Tifts6. Genetic variations of viruses Genetic variation of viruses modify their reaction to specific antibodies giving place to new strains of viruses. One distinguishes antigenic drifts and antigenic shifts. The mutation of the gens may be very small. They are point mutations, changing simple aminoacids of the HA and the N proteins.