a thymidine(6-4)thymidine in DNA = a thymidine dimer in DNA
a thymidine(6-4)thymidine in dna = a thymidine dimer in dna
a thymidine(6-4)thymidine in DNA = a thymidine dimer in DNA
a thymidine(6-4)thymidine in dna = a thymidine dimer in dna