Nonionizing radiation, such as UV light, causes covalent bonds to form between adjacent pyrimidine bases. This would most likely form a dimer of:
(A) Thymine and thymine
(B) Cystosine and cytosine
(C) Cytosine and thymine
(D) Uracil and cytosine
Answers
Explanation:
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Answer:
c cystosinr and thymine
Explanation:
Pyrimidine dimers are molecular lesions formed from thymine or cytosine bases in DNA via photochemical reactions.[1][2] Ultraviolet light (UV) induces the formation of covalent linkages between consecutive bases along the nucleotide chain in the vicinity of their carbon–carbon double bonds.[3] The dimerization reaction can also occur among pyrimidine bases in dsRNA (double-stranded RNA)—uracil or cytosine. Two common UV products are cyclobutane pyrimidine dimers (CPDs) and 6–4 photoproducts. These premutagenic lesions alter the structure and possibly the base-pairing. Up to 50–100 such reactions per second might occur in a skin cell during exposure to sunlight, but are usually corrected within seconds by photolyase reactivation or nucleotide excision repair. Uncorrected lesions can inhibit polymerases, cause misreading during transcription or replication, or lead to arrest of replication. Pyrimidine dimers are the primary cause of melanomas in humans.