Question: 148: Mad cow disease in cattle and Cr Jacob disease in humans are due to infection by \_\_\_\_ .
(1) Bacterium
(2) Virus
(3) Viroid
(4) Prion
Answer: Option (4)
Explanation:
Mad cow disease in cattle is known as Bovine Spongiform Encephalopathy, and Creutzfeldt–Jakob disease in humans is a similar neurodegenerative disorder.
Both diseases are caused by prions, which are infectious agents made only of protein and do not contain any nucleic acid such as DNA or RNA.
A prion is an abnormally folded protein that can induce normal proteins in the brain to change their shape and become abnormal.
These abnormal proteins accumulate in neural tissue, leading to degeneration of brain cells and formation of sponge-like holes in the brain.
Bacteria, viruses, and viroids contain genetic material, whereas prions are unique because they are composed solely of protein.
Therefore, the correct answer is prion.