单选题 The trp leader RNA contains four regions of complementary sequence 1, 2, 3 and 4, which are capable of forming alternative hairpin structures. which hairpin is the attenuator.

单选题 The strands of DNA are joined by ____ bonding between the bases on opposite strands, to form base pairs.

单选题 The base of DNA in A, G, C, ____ .

单选题 Pyrimidine dimers are the commonest product of ____ irradiation.

单选题 The pentose sugar of the DNA is ____ .

单选题 The leading strand and the lagging strand are englated by DNA polymerase ____ .

单选题 The final phosphodiester bond between the fragments is made by ____ .

单选题 The lagging strand primers are removed and the gaps filled by DNA polymerase ____ .

单选题 During the DNA replication the positive supercoiling formed by unwinding parents DNA hase to be relieved by the ____ .