<prompt> Ultraviolet light can damage a DNA strand causing:Two adjacent purine residue to form a covalently bounded dimerTwo adjacent pyrimidine residues to form covalently bonded dimerDisruption of phosphodiesterase linkageDisruption of non-covalent linkage  <response>: Ans. B. Two adjacent pyrimidine residues to form covalently bonded dimerDamage to DNA during its replication can occur from ultra violet irradiations that causes thymine dimer formation. 