Under the melting temperature, what happened to the DNA double helix:____
A. The double helix has been untied completely
B. The double helix has been untied about 50%
C. The UV absorption at 260nm increased
D. Part of hydrogen bonds between bases have been broken
E. All of the G-C base pairs disappeared
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Which of the following statements are correct about Tm value of DNA:____
A. It is directly related to the bases sequence order of DNA
B. It is related to the length of DNA
C. It is directly proportional to the percentage of G-C base pairs
D. The higher G+C/A+T value is, the higher Tm value is
E. Tm value represents the concentration of DNA after denaturation
DNA denaturation refer to:____
A. Depolymeriztion of polynucleotide chains
B. DNA molecule turns to double helix from supercoil
C. The phosphodiester bond in the DNA molecule has been broken
D. The hydrogen bond between bases has been broken
E. The complete hydrolysis of the nucleic acids
Which of the following statement is correct about the reason that nucleic acid has the ability to absorb UV:____
A. The conjugated double bond between purine and pyrimidine
B. Ribose is connected to purine and pyrimidine
C. There are nitrogen atoms inside purine and pyrimidine
D. Ribose and phosphate is connected to purine and pyrimidine
E. Phosphate group is connected to purine and pyrimidine
Which is the maximum UV absorption wavelength of nucleic acids:____
A. 280nm
B. 260nm
C. 240nm
D. 220nm
E. 490nm
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