Which of the following statements is incorrect ?

Options

A. Prions consist of abnormally folded protein
B. Viroids lack a protein coat.
C. Viruses are obligate parasites
D. Infective constituent in viruses is the protein coat.

Answer

To determine which statement is incorrect, we will analyze each of the four statements provided:

1. **Prions consist of abnormally folded proteins.**
- Prions are indeed infectious agents composed solely of protein. They are known for causing neurodegenerative diseases by inducing abnormal folding of normal cellular proteins. Therefore, this statement is **correct**.

2. **Viroids lack a protein coat.**
- Viroids are small, circular RNA molecules that do not have a protein coat, distinguishing them from viruses. They are known to infect plants. Thus, this statement is also **correct**.

3. **Viruses are obligate parasites.**
- Obligate parasites are organisms that can only reproduce within a host organism. Viruses fit this definition as they require a host cell to replicate and propagate. Hence, this statement is **correct**.

4. **Infective constituents in viruses is protein coat.**
- This statement is **incorrect**. The infective component of viruses is not the protein coat (capsid) but rather the genetic material (either DNA or RNA) that is delivered into the host cell to initiate infection.

Based on the analysis, the incorrect statement is the fourth one: "Infective constituents in viruses is protein coat."