Question

Which of the following causes mutation (not polyploidy)?
A. Crossing over
B. NaCl
C. Colchicine
D. $\gamma$- rays

Answer 1

Mutation can also be caused by exposure to specific chemicals or radiation. These types of agents cause the DNA to break down. Mutation can go either way; it can benefit organisms as well as it can harm organisms.

Complete step by step answer: Mutation is the process that produces a chromosome or gene, that is different from the wild type. Mutated gene or chromosome results from a mutational process, while mutant is the organism whose changed phenotype is attributed to a mutation. The mutation may result due to changes either on the chromosome or the gene. Among the other three physical mutagens, $\gamma$- rays are widely used. Reactive oxygen species (ROS) or free radicals can be generated in cells during the irradiation of the seeds with ionizing radiation to generate mutants with the desirable traits. $\gamma$- rays is recognised as a potent carcinogen due to its potential for oxidative damage. It causes a variety of lesions of DNA including single and double-stranded breaks, DNA-protein cross-links, oxidized bases and acidic sites.
i. Crossing over is a basic concept of genetics and cell biology often called recombination which occurs during meiosis.
ii. Various ions also play important roles in causing mutation like $N{a^ + }$and $C{l^ + }$.
iii. Colchicine hormone is a gene doubling hormone which plays a pivotal role in the process of mutation.
Hence, the correct answer is option D.

Note: Mutation maybe is of following types:
a. Gene mutation: It is a mutation where the allele of a gene changes.
b. Chromosome mutation: It is another type of mutation where changes take place in the segments of the chromosome.