Question

Given below are two statements:
Statement (I): Mutation is an important source of genetic variations existing in any organism.
Statement (II): The rate of mutations, however, is the same in both spontaneous and induced mutations.
In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

Induced mutation breeding is used in agriculture precisely because the spontaneous mutation rate is too low to find useful new traits in a reasonable timeframe.
Applying mutagens increases this rate, making it easier to identify beneficial mutants.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Mutations are heritable changes in the nucleotide sequence of an organism's genome.
They can occur naturally due to replication errors or environmental factors (spontaneous mutations) or can be deliberately caused by exposing tissues to physical or chemical mutagens (induced mutations).

Step 2: Detailed Explanation:
Let us analyze both statements:
1. Analysis of Statement (I): Mutations are the ultimate source of all genetic variation.
They introduce new alleles into a population's gene pool.
Other mechanisms of genetic variation, such as independent assortment, crossing over, and fertilization, simply recombine these existing alleles into new combinations.
Without mutation, evolutionary adaptation and crop improvement would be limited. Thus, Statement (I) is correct.
2. Analysis of Statement (II): Spontaneous mutations occur at an extremely low background rate, typically in the range of \( 10^{-5} \text{ to } 10^{-8} \) per gene per generation.
In contrast, induced mutations are generated by exposing seeds or plant tissues to mutagenic agents (such as EMS or gamma radiation).
These mutagens damage DNA or disrupt replication, increasing the mutation rate by several orders of magnitude (typically 10-fold to 10,000-fold compared to the spontaneous rate).
Therefore, the rate of mutation is significantly higher in induced mutations than in spontaneous mutations, making Statement (II) incorrect.

Step 3: Final Answer:
Statement (I) is correct, but Statement (II) is incorrect. This corresponds to option (C).