Determine the correctness or otherwise of the following Assertion (a) and the Reason (r). Assertion : N-methyl-N'-nitro-N-nitrosoguanidine (NTG) is an effective chemical mutagen. Reason: Mutations induced by NTG mainly are the GC $\rightarrow$ AT transitions.
Assertion Reason Analysis: NTG Mutagenicity
This section analyzes the Assertion (a) and Reason (r) concerning N-methyl-N'-nitro-N-nitrosoguanidine (NTG).
Evaluating Assertion (a)
Assertion: N-methyl-N'-nitro-N-nitrosoguanidine (NTG) is an effective chemical mutagen.
Analysis: This statement is true. NTG is widely recognized and utilized in scientific research as a potent chemical mutagen capable of inducing genetic mutations.
Evaluating Reason (r)
Reason: Mutations induced by NTG mainly are the GC $\rightarrow$ AT transitions.
Analysis: This statement is considered false. NTG acts as an alkylating agent that damages DNA, leading to replication errors. While GC $\rightarrow$ AT transitions are among the mutations it can cause, it is not accurate to state they are the *main* type. NTG can induce a broader spectrum of mutations, including other transitions and transversions.
Conclusion
According to the analysis:
- Assertion (a) is true.
- Reason (r) is false.
Therefore, the correct choice reflects that the assertion is true, but the reason is false.
Important Questions from Mutations and Mutagenesis
Determine the correctness or otherwise of the following Assertion [a] and the Reason [r].
Assertion [a]: Chromosome mutations can change the structure of chromosomes.
Reason [r]: All chromosome mutations arise due to nondisjunction of chromosomes during mitosis or meiosis.A DNA sequence, 5'-ATGGACGTGCTTCCCAAAGCATCGGGC-3', is mutated to obtain
P. 5'-ATGGACGTGCTTCaCAAAGCATCGGGC-3′
Q. 5′-ATGGACGTGCTTCCCgAAAGCATCGGGC-3′
R. 5'-ATGGACGTGCTTCC-AAAGCATCGGGC-3′
S. 5'-ATGGACGTGCTTCCCAAtGCATCGGGC-3′
T. 5'-ATGGACGaGCTTCCCAAAGCATCGGGC-3′
[Point mutations are shown in the lower case or ‘–' within the sequences]
Which of the above mutant sequences DO NOT have frame-shift?
- A mutation in a gene that codes for a polypeptide results in a variant polypeptide that lacks the last three amino acids. What type of mutation is this?
- A truncated polypeptide is synthesized due to a nonsense mutation. Where would you introduce another mutation to obtain a full-length polypeptide?
- Lysine is being produced in a lab-scale reactor by a threonine auxotroph. After 2 weeks of operation it was observed that the concentration of lysine in the reactor was gradually decreasing. Microbiological assays of reactor samples showed absence of contamination and recorded data showed no change in the operating conditions. The most probable reason for decrease in lysine concentration may be attributed to
