Determine the percentage of the other three nitrogenous bases

 To determine the percentage of the other three nitrogenous bases in a double-stranded DNA molecule containing 13.5% cytosine (C), we use Chargaff’s rule, which states:

• Cytosine (C) pairs with Guanine (G) → equal amounts of C and G
• Adenine (A) pairs with Thymine (T) → equal amounts of A and T
• Total percentage of all bases = 100%

Step-by-Step Calculation:

1. Cytosine (C) = 13.5%
2. Guanine (G) = 13.5% (since C = G)
3. Total percentage of C and G = 13.5% + 13.5% = 27%
4. Remaining percentage for A and T = 100% - 27% = 73%
5. Since A = T, divide by 2:
   • Adenine (A) = 73% ÷ 2 = 36.5%
   • Thymine (T) = 36.5%

Final Answer:

• Cytosine (C) = 13.5%
• Guanine (G) = 13.5%
• Adenine (A) = 36.5%
• Thymine (T) = 36.5%