12. Define the following II

a. Vaccines are preparation of  killedliving or killedliving  microorganisms or their products used to prevent or treat diseases.

 

b. Preparation of antigenic proteins of pathogens on inoculation into a healthy person provides permanent immunitytemporary or permanent immunitytemporary immunity against a particular disease.

 

The word 'prion' means proteinaceous infectiousnon infectious particle, i.e., pathogenic viral particles containing only proteins. But they do not contain nucleic acidproteins. They are the rod-shaped cell surface glycoprotein found in neurons.