Where do prions come from?
a. there are prion-like particles in the brain normally, and when these become abnormal they can cause disease.
b. mosquitoes.
c. they are clumps which form from normal prion-like particles in the blood that travel to the brain.
d. they are introduced by infectious protozoa.
e. contaminated water.

There are prion-like particles in the brain normally, and when these become abnormal they can cause disease. (Ans. A)

Explanation:

Prions are proteins which can trigger normal proteins to fold abnormally, and they are present in the brain. They are causing many types of neurodegenerative diseases in both humans and animals. Which are known as transmissible spongiform encephalopathies.

Prions can enter the brain with the help of infection, also can arise from the gene mutation that encodes the proteins, and sometimes this affects humans by infected meat.

If a person infected from prion disease, it affects central nervous system tissues like brain, eye tissues and spinal cord.