Final answer:
The type of DNA mutation caused by exposure to chemicals or UV radiation is an induced mutation. These mutations occur when environmental factors act as mutagens, affecting the DNA's nucleotide sequence and can include the formation of thymine dimers due to UV exposure.
Step-by-step explanation:
The type of DNA mutation caused by exposure to chemicals or UV radiation is induced. Mutations to the nucleotide sequence of DNA can occur in two main ways: they can either be spontaneous, occurring without any external environmental influence, or they can be induced, resulting from environmental agents such as chemicals, ultraviolet (UV) rays, and x-rays. Exposure to these mutagens can damage DNA by altering the chemical structure of nucleotides or by causing breaks in the DNA strand, which can lead to incorrect base pairing during DNA replication.
Induced mutations specifically occur due to environmental factors including radiation or chemical exposure. During such exposure, for instance, UV radiation causes adjacent thymine bases to bond together, forming thymine dimers that create a bulge in the DNA molecule. If this bulge isn't repaired, it can result in permanent mutations that compromise the integrity of the genetic information during replication, transcription, and translation processes.
Environmental factors known as mutagens are common causes of induced mutations, which are different from spontaneous mutations that result from errors in normal cellular processes such as DNA replication. The distinction is important as induced mutations can greatly increase the mutation rate and may also lead to health risks such as cancer, given that many mutagens can also be carcinogens.