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How can ultraviolet light, X-rays, and certain chemicals cause mutations?

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Four kittens with different fur patterns-three tabby and one black-and-white-lying together in a box, illustrating genetic variation among offspring. — heredity Each offspring is a combination of its two parents, receiving some dominant traits from its mother and others from its father.

Ultraviolet (UV) light, X-rays, and various chemicals act as mutagens by physically or chemically altering the structure of DNA, which can lead to errors during replication.12

Ultraviolet (UV) Light

UV radiation primarily causes mutations by inducing the covalent linking of adjacent pyrimidine bases, creating pyrimidine dimers. This structural distortion blocks normal DNA replication. Additionally, UV light can facilitate photosensitization, where energy is transferred to molecular oxygen to create reactive "singlet oxygen" that attacks DNA.34

X-rays

As a form of ionizing radiation, X-rays can break both strands of the DNA molecule. These double-strand breaks can lead to chromosome deletions or translocations, where broken ends rejoin incorrectly, altering gene sequences. X-rays also generate free radicals within the cell that cause oxidative damage to bases, such as guanine.54

Chemicals

Chemical mutagens alter DNA through several mechanisms:
* Base Modification: Agents like nitrous acid or halogens react directly with bases, changing their chemical structure and causing incorrect base pairing.6
* Alkylation: Compounds like nitrosamines add alkyl groups to DNA, interfering with replication.4
* Oxidative Damage: Strong oxidizing agents create free radicals that damage DNA bases.64