If Meselson and Stahl's experiment is continued for four generations in bacteria, the ratio of `overset(15)N//overset(15)N: overset(15)N//overset(14):overset(14)//overset(14)N` containing DNA in the fourth generation would be

Options

A. `1:1:0`
B. `1:4:0`
C. `0:1:3`
D. `0:1:7`

Answer

D

Explanation

Meselson and Stahl found that DNA of the first generation was hybrid or intermediate `(.^15N" and ".^14N)` The second chloride at a level higher then the fully labelled DNA of parent bacteria `(.^15N ^14N)`The secound generation of bacteria after 40 minutes, conetained two types of DN, 50% light `(N^(15)N^(14))`.
The thrid generation of bacteria after 60 minutes contained two types of DNA, 25% intermediate `(N^(15)N^(14))`and 75% light `(N^(14)N^(14))` in `1:3` ratio. Two fourth generation after 80 80 minutes contained 12.5% `(N^(15)N^(14))` and 87.5%`(N^(14)N^(14))` DNA in `1:7` ratio