During cultivation of E.coli, the spontaneous point mutations are largely caused by:()
A. The tautomeric shift of hydrogen atom
B. The broken of DNA sugar-phosphate backbone
C. The insertion of one base-pair
D. The cross-linking of inter-strands
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The most common form of ultraviolet irradiation-induced DNA damage is the generation of thymine dimer. Which of the following statement is correct about changes of DNA structure in this process:()
A. It is the covalent linkage between thymines of the two complementary polynucleotide chain
B. It can be repaired by the relevant enzyme system including nucleotide excision repair system
C. It is catalyzed by thymine dimeric enzyme
D. It will not affect DNA replication process
Single-base substitution is a kind of DNA damage, they can:()
A. affect transcription process instead of replication
B. affect DNA sequence but not DNA secondary structure
C. change DNA double helix structure but won’t affect replication process
D. be induced by ultraviolet irradiation(such as pyrimidine dimer)or the formation of additive compound (such as alkylation)
The damage of ultraviolet irradiation to DNA mainly is:()
A. Base substitution
Broken of phosphodiester bond
C. Deletion of base
D. Formation of covalent pyrimidine dimer
Which of the following belongs to spontaneous damage of DNA:()
A. Single-base mismatch during DNA replication
B. Formation of thymine dimer
Cytosine deoxidation
DNA cross-linking
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