85. A big fire broke out last night, as a c______________, the house was burnt to the ground.

84. Only two passengers s_________ the air-crash.

83. My job is different from anyone else’s, so my job is u__________..

82. He was a_________ as president of the meeting.

51. ⑴     A                 ATCGCTTCTTTC  

⑵ [  2 ]  核糖体    [ 3  ] mRNA      [  1 ]   tRNA              多肽（蛋白质）     

50. ⑴    胸腺嘧啶       ⑵      胞嘧啶              氢键       

 ⑶          胸腺嘧啶脱氧核苷酸                   多脱氧核苷酸链       

49. ⑴  Ⅰ         染色体畸变      杂交育种   ⑵    花药离体培养     秋水仙素  

⑶       12.25%         

48. ⑴      基因库      （2）        65%                     35%          

47. ⑴    减Ⅰ后期                 ⑵     有丝分裂后期    （3）   减Ⅱ后期