Guanine

Definition

Guanine is one of the four primary nitrogenous bases found in DNA and RNA, represented by the letter 'G'. It pairs specifically with cytosine through three hydrogen bonds, which contributes to the stability of the DNA double helix structure. As a key component of nucleotides, guanine plays a vital role in the encoding of genetic information and is essential for various cellular processes.

5 Must Know Facts For Your Next Test

1. Guanine is synthesized from xanthosine monophosphate (XMP) in cells and is vital for nucleotide formation.
2. In DNA, guanine forms three hydrogen bonds with cytosine, making this pair one of the strongest in the double helix structure.
3. Guanine can also exist in different tautomeric forms, which can affect its pairing during DNA replication.
4. Mutations involving guanine can lead to various genetic disorders if they occur in critical regions of genes.
5. In RNA, guanine pairs with cytosine just like in DNA, but it also pairs with uracil when forming RNA strands.

Review Questions

• How does guanine's pairing with cytosine contribute to the overall stability of the DNA double helix?
  • Guanine pairs with cytosine through three hydrogen bonds, which provides stronger interactions compared to the two hydrogen bonds formed between adenine and thymine. This increased bonding strength between guanine and cytosine enhances the stability of the DNA double helix structure, making it less susceptible to denaturation. This stability is crucial for maintaining the integrity of genetic information during processes such as replication and transcription.
• Discuss the significance of guanine in the context of nucleotide structure and function in both DNA and RNA.
  • Guanine is an essential nitrogenous base that serves as a key component of nucleotides, which are the building blocks of DNA and RNA. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base like guanine. In both DNA and RNA, guanine is involved in encoding genetic information through complementary base pairing. Its role in nucleotide structure ensures proper formation of nucleic acids, facilitating processes like replication and transcription.
• Evaluate how mutations involving guanine can impact genetic stability and contribute to disease.
  • Mutations involving guanine can lead to significant changes in genetic sequences, potentially resulting in altered protein functions or gene expression. If these mutations occur in critical regions such as coding sequences or regulatory elements, they can disrupt normal cellular functions and contribute to various diseases, including cancer. The presence of tautomeric forms of guanine can also influence pairing during replication, further increasing the likelihood of mutations that affect genetic stability.

Related terms

Cytosine:

A nitrogenous base that pairs with guanine in the DNA double helix, contributing to the overall stability and structure of nucleic acids.

Nucleotide: The basic building block of DNA and RNA, composed of a nitrogenous base (such as guanine), a sugar molecule, and a phosphate group.

Complementary Base Pairing: The specific pairing of nitrogenous bases in DNA and RNA, where adenine pairs with thymine (or uracil in RNA) and guanine pairs with cytosine.