g UV radiation causes covalent dimerization of two subsequent bases in DNA. This dimer is recognized and repaired by .

The options are not given.

Here are the options.

a. C and C DNA photolyase

b. T and T DNA photolyase

c. C and C DNA photoisomerase

d. T and T DNA photoisomerase

e. None of the above

Explanation:

UV light damages the DNA of cells that are exposed by making bonds to be formed between adjacent pyrimidine bases, usually thymines, in the DNA chains. The thymine dimers inhibit or hinder the DNA correct replication during reproduction of the cell.

UV radiation causes covalent dimerization of two subsequent T and T because Thymine bases of DNA directly absorbs a UVB photon . UVB light causes thymine base pairs close to each other in genetic sequences to bond together into pyrimidine dimers, thereby causing a disruption in the strand, which reproductive enzymes cannot copy.

UV-induced thymine dimers can be repaired by photoreactivation, in a process where energy from visible light is used to split the bonds forming the cyclobutane ring through the action of DNA photolyase, an enzyme that repaired damaged cause by uv radiation to dna.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.

the answer is cell division : )