E. coli with completely N15 DNA was allowed to replicate in N14 medium for two generations. Percentage of bacteria with heavy DNA will be

Question

E. coli with completely N15 DNA was allowed to replicate in N14 medium for two generations. Percentage of bacteria with heavy DNA will be (A) 6.25 % (B) 50 % (C) 25 % (D) 100 %

Tardigrade Admin · Accepted Answer

Meselson and Stahl found that the DNA of the first generation of bacteria was hybrid or intermediate ( N 14 N 14). The second generation of bacteria, after 40 minutes, contained two types of DNA, 50 % light ( .N 14 N 14) and 50 % intermediate ( N 14 N 15). The third generation of bacteria after 60 minutes contained two types of DNA, 25 % intermediate ( .N 15 N 14) and 75 % light (N14 N14) in a 1: 3 ratio. The fourth-generation after 80 minutes contained 12.5 % N 15 N 14 and 87.5 % N 14 N 14 DNA in a 1:7 ratio.

Q. E. coli with completely $N^{15}$ DNA was allowed to replicate in $N^{14}$ medium for two generations. Percentage of bacteria with heavy DNA will be

$6.25%$

$50%$

$25%$

$100%$

Q. E. coli with completely N15 DNA was allowed to replicate in N14 medium for two generations. Percentage of bacteria with heavy DNA will be

6.25%

50%

25%

100%

Q. E. coli with completely $N^{15}$ DNA was allowed to replicate in $N^{14}$ medium for two generations. Percentage of bacteria with heavy DNA will be

$6.25%$

$50%$

$25%$

$100%$