In a DNA or RNA strand, nucleotides join together to form a sugar phosphate backbone. These nucleotides are linked to each other by covalent bonds between which components of adjacent nucleotides?

Introduction / Context:
Nucleic acids such as DNA and RNA are long polymers made up of repeating nucleotide units. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. Understanding how these nucleotides are linked together to form a continuous strand is essential for grasping the structural stability of DNA and RNA. This question tests your knowledge of which parts of adjacent nucleotides are joined by covalent bonds to create the sugar phosphate backbone.

Given Data / Assumptions:

• Nucleotides are the building blocks of DNA and RNA.
• Each nucleotide has a sugar, a phosphate group, and a nitrogenous base.
• The question is about the covalent linkage between neighboring nucleotides in a strand.
• Options mention bonds between phosphate, sugar, bases, and amino acids.

Concept / Approach:
In nucleic acid strands, nucleotides are connected by phosphodiester bonds. These covalent bonds form between the phosphate group attached to the 5 prime carbon of one sugar and the hydroxyl group on the 3 prime carbon of the sugar in the next nucleotide. Thus, the phosphate group of one nucleotide links to the sugar of the next, creating a sugar phosphate backbone. The nitrogenous bases project from this backbone and pair with complementary bases on the opposite strand in double stranded DNA, but they are not directly involved in forming the backbone linkages.

Step-by-Step Solution:
Step 1: Recall that a nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. Step 2: Visualize the sugar phosphate backbone of DNA or RNA as a repeating pattern of sugar phosphate sugar phosphate along the strand. Step 3: Remember that phosphodiester bonds connect the 5 prime phosphate group of one nucleotide to the 3 prime hydroxyl group of the next sugar. Step 4: Recognize that this means the phosphate group of one nucleotide is covalently bonded to the sugar of the next nucleotide. Step 5: Choose the option that accurately describes this sugar phosphate linkage.

Verification / Alternative check:
Textbook diagrams of DNA structure often label the backbone as a series of linked sugars and phosphates, with bases extending outward. They show arrows or lines from the phosphate on one nucleotide connecting to the sugar on the next nucleotide. This arrangement is described as a phosphodiester bond because it involves phosphate (phospho) and two ester linkages with sugar molecules (diester). These diagrams clearly show that bases are not the elements forming the backbone bonds between nucleotides, confirming that the sugar phosphate linkage is correct.

Why Other Options Are Wrong:
The nitrogenous bases of adjacent nucleotides only: Bases pair with complementary bases on the opposite strand via hydrogen bonds, not covalent bonds in the backbone. The phosphate groups of two neighboring nucleotides directly: Phosphates do not directly bond to each other in the backbone; they connect through sugars. The sugar groups of neighboring nucleotides without any phosphate: Sugars are not directly bonded to each other; the phosphate group forms the bridge. Amino acid side chains attached between nucleotides: Amino acids form proteins, not nucleic acid backbones, so this option is unrelated.

Common Pitfalls:
Students may confuse the hydrogen bonds that hold complementary base pairs together with the covalent bonds in the backbone. Hydrogen bonds are relatively weak and allow DNA strands to separate during replication and transcription. In contrast, phosphodiester bonds are strong covalent bonds that maintain the integrity of each strand. Keeping this distinction clear will help you correctly identify that the backbone bonds join the phosphate of one nucleotide to the sugar of the next.

Final Answer:
Nucleotides in a DNA or RNA strand are attached by covalent bonds between The phosphate group of one nucleotide and the sugar of the next nucleotide.