A genetics student was asked to draw the chemical structure of an adenine- and thymine-containing dinucleotide derived from DNA. The answer is shown here: The student made more than six major errors. One of them is circled, numbered 1, and explained. Find five others. Circle them, number them 2 through 6, and briefly explain each in the manner of the example given.

Key Concepts

Nucleotide Structure

Nucleotides are the building blocks of DNA and RNA, consisting of a phosphate group, a sugar (deoxyribose in DNA), and a nitrogenous base (adenine, thymine, cytosine, or guanine). Understanding the structure of nucleotides is essential for accurately drawing dinucleotides, as errors in the arrangement or components can lead to incorrect representations.

Base Pairing Rules

In DNA, adenine pairs with thymine through two hydrogen bonds, while cytosine pairs with guanine through three hydrogen bonds. Familiarity with these base pairing rules is crucial for identifying errors in the structure of a dinucleotide, as incorrect pairings can significantly alter the chemical representation and biological function of the molecule.

Phosphodiester Bond

Phosphodiester bonds link nucleotides together in a DNA strand, forming the backbone of the molecule. This bond occurs between the phosphate group of one nucleotide and the hydroxyl group of the sugar of another. Recognizing the correct formation and orientation of these bonds is vital for accurately depicting the dinucleotide structure and understanding its stability and function.