Question

Escherichia coli cells were grown for many generations in ¹⁵NH₄CI as sole nitrogen source. Subsequently, these cells were grown exactly for four generations in medium containing ¹⁴NH₄CI. The DNA from these cells were isolated and separated. It ¹⁵N/¹⁵N represents the two strands of DNA where both strands have heavy nitrogen; ¹⁵N/¹⁴N as intermediate DNA; and ¹⁴N/¹⁴N as DNA containing light nitrogen, the ratios for heavy: intermediate: light DNA, respectively would be

• A. 1 : 0 : 7
• B. 1 : 1 : 6
• C. 0 : 1 : 7
• D. 0 : 8 : 0

Answer 1

Answer: (C)

0 : 1 : 7