The 5' end of a DNA molecule can be chemically distinguished from the 3' end because there is a(n)__________ group at the 5' end and a(n)__________ group at the 3' end.
A) NH₃; COOH
B)PO₄; SO₄
C)OH; H
D)PO₄; OH
E)none of the aboᵥe

Question

Quizplus · Accepted Answer

The phosphate group (PO₄) is present at both the 5' and 3' ends of a DNA molecule, but it is only covalently bonded to a deoxyribose sugar at the 5' end. Therefore, the 5' end is distinguished by the presence of a free phosphate group (PO₄), while the 3' end is distinguished by the presence of a hydroxyl group (-OH) attached to the 3' carbon of the deoxyribose sugar. Choice D is the only option that includes both of these groups as distinguishing features.

The 5' End of a DNA Molecule Can Be Chemically