Which conclusion can be drawn from the experimental observation that a single strand of DNA contains 2100 dA residues and 1800 dT residues?
A) There must have been some loss of material in the extraction because the number of dA and dT residues must be the same.
B) This is a palindromic sequence.
C) There must be 2100 dT and 1800 dA residues on the complementary strand.
D) none of these

Question

Quizplus · Accepted Answer

The complementary strand of DNA is antiparallel and matches up with the opposite nucleotide bases. Therefore, the number of dT residues on the complementary strand should match the number of dA residues on the original strand and vice versa. The observation that there are 2100 dA residues and 1800 dT residues suggests that the complementary strand contains 2100 dT residues and 1800 dA residues to match up with the original strand. This is known as Chargaff's rule. Option A is incorrect because it assumes that the number of dA and dT residues must be the same, which is not true. Option B is incorrect because palindromic sequences have a specific symmetry that is not present in this observation.

Which Conclusion Can Be Drawn from the Experimental Observation That