If Meselson and Stahl's experiment is continued for sixth generations in bacteria, the ratio of Heavy strands `""^(15)N//""^(15)N`: Hybrid `""^(15)N//""^(14)N` : light `""^(14)N//""^(14)N` containing DNA in the sixth generation would be

Options

A. `1:1:1 `
B. `0:1:7 `
C. `0:1:15 `
D. `0:1:31 `

Answer

D

Explanation

In generation only `""^(15)N` is pres ent as it was there before the transportation of bacteria to light nitrogen. Generation 1 has intermediates only `(""^(15)N^(14)N)` illustrating hybrid formation. Generation 2 produces two strands one intermediate and other lighter band `(""^(15)N^(14)N)` and N14 in equal proportion, so the ratio is 1:1. Generation 3 forms two bands one thin hybrid or an intermediate band and other thick light bands, so the ratio is 1:3.
Generation 4 leads to the production of two bands, a thinner intermediate band and thicker lighter band in the ratio 1:7. The penultimate generation will lead to the production of two bands, one thin hybrid or an intermediate band and other thick light bands in the ratio 1:31.
Hence, the final ratio will be `0:1:31`.