Determine the correctness or otherwise of the following Assertion (a) and the Reason (r) Assertion: Isopropylthiogalactoside (IPTG) is a gratuitous inducer of lactose operon. Reason: Gratuitous inducers are chemical analogs which behave like natural inducer but they do not serve as substrate for the enzymes that are subsequently synthesized.
both (a) and (r) are true and (r) is the correct reason for (a)
Assertion (a) Correctness: IPTG as Gratuitous Inducer
The Assertion states that Isopropylthiogalactoside (IPTG) is a gratuitous inducer of the lactose operon. This statement is TRUE. IPTG effectively binds to the Lac repressor protein, causing it to detach from the operator region of the DNA. This allows transcription of the lactose operon genes (lacZ, lacY, lacA) to begin. Crucially, IPTG itself is not metabolized by the enzymes produced by the lac operon, such as beta-galactosidase.
Reason (r) Correctness: Definition of Gratuitous Inducer
The Reason defines a gratuitous inducer as a chemical analog that mimics the natural inducer but is not a substrate for the enzymes synthesized by the operon. This definition is also TRUE. This property is key to why such molecules are useful tools in molecular biology; they induce gene expression without being consumed or altered by the process.
Relationship Between Assertion and Reason
The reason accurately explains why the assertion is correct. IPTG functions as a gratuitous inducer precisely because it fits the definition provided in the reason: it behaves like the natural inducer (allolactose) by binding to the repressor, but it is not broken down by the resulting enzymes (like beta-galactosidase). Therefore, the reason is the correct explanation for the assertion.
Conclusion
Both the Assertion (a) and the Reason (r) are factually correct, and the Reason (r) correctly explains why the Assertion (a) is true.
Important Questions from Regulation of Gene Expression
- Which of the following conditions induce(s) the expression of $ \beta$-galactosidase gene in the lac operon?
Determine the correctness or otherwise of the following Assertion [a] and the Reason [r].
Assertion [a]: In multicellular organisms, cells of different lineages have different gene expression profiles.
Reason [r]: Alternative splicing is the only mechanism to generate protein diversity.- The event(s) that lead(s) to inactivation of tumor suppressor genes in cancer cells is(are)
- Which of the following statement(s) is(are) CORRECT regarding the $lac$ operon in $E. coli$ when grown in the presence of glucose and lactose?
Determine the correctness or otherwise of the following Assertion [a] and the Reason [r]
Assertion: Ab initio gene finding algorithms that predict protein coding genes in eukaryotic genomes are not completely accurate.
Reason: Eukaryotic splice sites are difficult to predict.
