Mutations caused by external agents like chemicals or radiation are called what?

• A. Mutagen
• B. Genome
• C. Frameshift mutation
• D. Polyploidy

Answer: (A)

Mutagens are agents from the environment that increase the occurrence of mutations by damaging DNA or interfering with its replication. They can be chemical or physical. Chemical mutagens may alter bases, cause mispairing, or cause insertions and deletions, leading to substitutions or frameshift mutations. Physical mutagens like UV light can form thymine dimers that distort the DNA structure and cause errors during replication, while X-rays can create breaks in DNA strands, potentially causing larger chromosomal changes. Because they drive changes in the DNA, these external agents are described as mutagens.