In the “Ac-Ds” system in maize, which of the following is correct about “Ds”（）
A. It is an autonomous controlling element
B. It is an activator
C. It does not contain terminal inverted repeats
D. It contains incomplete transposase gene
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Which of the following mutagen leads to frameshift mutation（）
A. Base analogs
B. Alkylating agents
C. Nitrite
D. Intercalating agents
In photo-reactivation, DNA damage caused by UV light is reversed by DNA photolyase which（）
A. is activated by UV light to form a complex
B. removes nicks in the DNA backbone
C. forms a complex with thymine dimers and the complex absorbs visible light which reverses the dimerization
D. binds to the adenine bases opposite the thymine dimer
DNA replication in eukaryotes（）
A. usually starts at the same place every time
B. only involve 2 different DNA polymerases
C. is faster than in bacterial DNA replication
D. all of the above are false
Transposition（）
Also requires homology between sequences
B. Occurs only in prokaryotes
C. Was firstly discovered by Sanger
D. Needs transposase to catalyzes the insertion
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