Question

Which is not a nucleotide base in DNA? a. adenine b. guanine c. glutamine d. thymine e. cytosine

Short answer

Glutamine is not a nucleotide base in DNA.

Step-by-step solution

Identify Nucleotide Bases in DNA

DNA is composed of four nucleotide bases: adenine (A), guanine (G), cytosine (C), and thymine (T). These bases pair specifically, with adenine pairing with thymine and guanine pairing with cytosine.

Compare Given Options

The options given are adenine, guanine, glutamine, thymine, and cytosine. Recall that the nucleotide bases of DNA are adenine, guanine, cytosine, and thymine only.

Identify Non-Nucleotide Base

Among the options, adenine (a), guanine (b), thymine (d), and cytosine (e) are nucleotide bases in DNA. Glutamine (c) is an amino acid, not a nucleotide base.

Key concepts

Adenine

Adenine is one of the four essential nucleotide bases found in the DNA molecule. It is represented by the letter "A". This base is a purine, which is characterized by a double-ring structure.
Adenine plays a crucial role in DNA pairing and stability by forming two hydrogen bonds with thymine ("T"), its complementary base.
This specific pairing mechanism is fundamental to the DNA double helix structure, ensuring genetic information is accurately replicated and transmitted.
Apart from its role in DNA, adenine is also a building block in ATP (adenosine triphosphate), the energy currency of the cell.

• Belongs to purine class.
• Pairs with thymine.
• Involved in cellular energy processes.

Guanine

Guanine is represented by the letter "G" and is another purine nucleotide base in DNA. Like adenine, guanine has a double-ring structure but it is unique in its pairing behavior.
It specifically pairs with cytosine ("C"), forming three hydrogen bonds. This combination provides stronger stability and integrity to the DNA strand.
Guanine is not only important for the genetic function of DNA, but it also plays roles in various cellular processes through its presence in GTP (guanosine triphosphate), a molecule similar to ATP.
Understanding guanine is essential for grasping the precise mechanisms of DNA replication and transcription.

• Purine base.
• Forms three hydrogen bonds with cytosine.
• Key in DNA stability and cellular signaling.

Thymine

Thymine, denoted by the letter "T", is one of the pyrimidine bases in DNA. Unlike purine bases, thymine has a single-ring structure.
It pairs exclusively with adenine ("A") by forming two hydrogen bonds. This pairing is critical for DNA replication and the accurate transmission of genetic information.
Thymine is distinctively found only in DNA, whereas in RNA, uracil takes its place. This characteristic makes thymine a pivotal component in distinguishing DNA from RNA.

• Pyrimidine class member.
• Pairs with adenine.
• Present only in DNA, not RNA.

Cytosine

Cytosine, represented by "C", is the second member of the pyrimidine family of nucleotide bases in DNA. It has a single-ring structure, similar to thymine.
Cytosine pairs with guanine ("G") through three hydrogen bonds, offering strong connectivity and stability to the DNA structure.
This robust pairing is vital for preventing mutations during DNA replication. In addition, cytosine plays a role in gene expression regulation and is sometimes involved in cellular processes like methylation.
In RNA, cytosine maintains its role as a fundamental component of the genetic sequence.

• Single-ring pyrimidine base.
• Pairs strongly with guanine.
• Involved in both DNA and RNA processes.