You are participating in a study group preparing for an upcoming genetics exam, and one member of the group proposes that each of you draw the structure of two DNA nucleotides joined in a single strand. The figures are drawn and exchanged for correction. You receive the accompanying diagram to correct: What is wrong with the way the nucleotides are joined?

Key Concepts

DNA Structure

DNA is composed of nucleotides, each consisting of a phosphate group, a sugar (deoxyribose), and a nitrogenous base. The nucleotides are linked together by phosphodiester bonds, which connect the phosphate group of one nucleotide to the sugar of the next. This creates a sugar-phosphate backbone that is essential for the stability and integrity of the DNA strand.

Phosphodiester Bond

A phosphodiester bond is a type of covalent bond that forms between the phosphate group of one nucleotide and the hydroxyl group on the sugar of another nucleotide. This bond is crucial for linking nucleotides in a DNA strand, allowing for the formation of a continuous chain. If the nucleotides are incorrectly joined, it may indicate a misunderstanding of how these bonds are formed.

Antiparallel Orientation

In a DNA strand, the two strands run in opposite directions, known as antiparallel orientation. One strand runs from the 5' to 3' direction, while the complementary strand runs from 3' to 5'. This orientation is vital for the proper pairing of bases and the overall stability of the DNA double helix. Any error in the joining of nucleotides may disrupt this orientation.