Which the following is false about the supercoil structure of DNA:____
A. It’s the character of closed circular DNA (Once a single strand or double strands break, the supercoil of DNA is destroyed)
B. Topoisomerases in the cell can regulate the level of supercoil of DNA.
C. The formation of DNA supercoil needs DNA ligase.
D. Almost all DNA molecules in the cell is negatively supercoiled.
E. The level of supercoil of DNA is regulated by topoisomerases.
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Which the following is false about the tertiary structure of DNA:____
A. Kink of the chain
B. Supercoil
C. Loops formed within a single strand of DNA
D. Concatenated circle in circular DNA
E. Double helix of DNA
Which of the following is correct about the nitrogen bases in DNA: ____
A=G, C=T
B. The composing and ratio of bases in DNA is different in different organisms.
C. The composing and ratio of bases in DNA is different in different organs of one organism.
D. The composing of bases in DNA is constant with the age increase.
E. Uracil is included in DNA.
Which of the following is right about the double helix structure of DNA: ____
A=T
B. Nitrogen bases face the inside of double helix in DNA.
C. 10bp per turn, the pitch is 3.4nm in double helix.
D. Horizontally, DNA stability is maintained by hydrogen bond between base pairs.
E. Vertically, DNA stability is maintained by base stacking force.
The force contributing to DNA stability mainly include: ____
A. phosphodiester
B. hydrogen bond between base pairs
C. base stacking force
D. the support of phosphate backbone
E. the repulsive force of negatively charged phosphate backbone
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