Question

DNA isolated from a cell in a sea urchin was found to have 32 percent adenine. Based on this data, which of the following can be determined about the composition of the sea urchin's DNA?

• A. The DNA contains 32 percent cytosine
• B. The DNA contains 68 percent thymine
• C. The DNA contains 32 percent guanine
• D. The DNA contains 68 percent guanine
  
• E. The DNA contains 32 percent thymine

Answer 1

The correct option is E The DNA contains 32 percent thymine

Amount of adenine (A) = 32%

Since amount of adenine is equal to thymine, therefore, amount of thymine (T) = 32%

A + T = 32 + 32 = 64%

Since (A + T) + (G + C) = 100%, therefore, G + C = 100 - 64 = 36%

Amount of cytosine (C) is equal to guanine (G), therefore, C = G = 36/2 = 18%

Hence the option E is showing the right conclusion about the composition of the sea urchin's DNA.

So, the correct answer is 'The DNA contains 32 percent thymine'.