Final answer:
UV irradiation causes neighboring pyrimidines on a DNA strand to dimerize, often resulting in the formation of thymine dimers. These dimers can disrupt DNA replication and transcription if not repaired, potentially leading to mutations.
Step-by-step explanation:
When DNA is exposed to UV irradiation, it can cause neighboring pyrimidines, which are the components of the nucleic acids that make up DNA, to undergo a process known as dimerization. Specifically, thymine dimers are the most common type of damage where two adjacent thymine bases bond covalently. This event distorts the DNA molecule's structure, potentially resulting in disruption to DNA replication and transcription processes. If these dimers are not properly repaired through a mechanism called nucleotide excision repair, they can lead to mutations which may have various biological consequences. Uncorrected, a thymine dimer could result in a deletion of the affected bases during DNA replication.