Consider the following statements and choose the correct answer using the codes given below :
Assertion [A]: Mycoplasma lacks a cell wall.
Reason [R]: Mycoplasma are resistant to antibiotics that target cell wall synthesis.

Question

Consider the following statements and choose the correct answer using the codes given below : 
Assertion [A]: Mycoplasma lacks a cell wall. 
Reason [R]: Mycoplasma are resistant to antibiotics that target cell wall synthesis.

Accepted Answer

The correct option is (2): Both A and R are true but R is not the correct explanation of A

This option correctly assesses the factual accuracy of both statements while accurately distinguishing between a cause and a consequence. Assertion $$A$$ states that *Mycoplasma lacks a cell wall*, which is an established, fundamental biological fact about this genus, the smallest known free-living bacteria. They are unique among bacteria in that their cell membrane is not protected by the rigid peptidoglycan layer, allowing them to take on various shapes, a phenomenon known as pleomorphism. Reason $$R$$ states that *Mycoplasma are resistant to antibiotics that target cell wall synthesis*. This is also a correct statement. Antibiotics like Penicillin and its derivatives (e.g., cephalosporins) function by interfering with the synthesis of the peptidoglycan layer. Since Mycoplasma does not possess this target structure, the antibiotics have no mechanism of action against them, resulting in inherent resistance. While R is a direct, logical *consequence* of A (resistance is due to the lack of the target), R does not serve as a biological *explanation* for A. The actual reason why Mycoplasma lacks a cell wall would be a matter of genetic and evolutionary biology (the loss of genes for cell wall synthesis), which the statement R does not address. Thus, both statements are true, but the Reason is a result of the Assertion, not a causal explanation for its existence.

The incorrect option is (1): Both A and R are true but R is the correct explanation of A

This option is incorrect because it misinterprets the cause-and-effect relationship between the Assertion and the Reason. While the two statements are logically connected in a conditional sense (If A, then R), the Reason is merely a demonstrable *effect* or *consequence* of the Assertion, not the fundamental biological *reason* for the Assertion itself. The clinical resistance to antibiotics (R) is an outcome of Mycoplasma's lack of a cell wall (A). The correct explanation for *why* Mycoplasma lacks a cell wall must be rooted in its evolutionary or genetic history, which R does not provide.

The incorrect option is (3): A is true but R is false

This option is incorrect because Reason [R] is a factually correct and critical piece of information in microbiology. Mycoplasma's resistance to beta-lactam antibiotics (which target cell wall synthesis) is why these drugs are ineffective in treating Mycoplasma infections. If R were false, it would mean that drugs like Penicillin would successfully kill Mycoplasma, which contradicts decades of clinical and laboratory evidence. Therefore, R is true, rendering this option invalid.

The incorrect option is (4): A is false but R is true

This option is incorrect because Assertion [A] is a defining, factually correct characteristic of the Mycoplasma genus. The absence of the peptidoglycan cell wall is the main feature that separates Mycoplasma from other bacteria and gives them their unique structural properties. For A to be false would mean that Mycoplasma possesses a cell wall, which is fundamentally incorrect according to their taxonomic classification. Since A is true, this option is invalid.