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08/01/2022 6:58 pm
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If Meselson and Stahl’s experiment is continued for four generations in bacteria, the ratio of 15N/ 15N : 15N/ 14N : 14N/14N containing DNA in the fourth generation would be
(a) 1 : 1 : 0
(b) 1 : 4 : 0
(c) 0 : 1 : 3
(d) 0 : 1 : 7
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08/01/2022 7:00 pm
Correct answer: (d) 0 : 1 : 7
Explanation:
If Meselson and Stahl’s experiment is continued for four generations in bacteria, the ratio of 15N/ 15N : 15N/ 14N : 14N/14N containing DNA in the fourth generation would be 0 : 1 : 7.
After third generation (60 min.) bacteria contains 25% hybrid (15N14N) in 1 :3 ratio. After 4th generation (80 min.) bacteria contains 12.5% hybrid and 87.5% light DNA in 1 : 7 ratio.