Cytosine

Definition

Cytosine is one of the four primary nitrogenous bases found in DNA and RNA, represented by the letter 'C'. It pairs specifically with guanine (G) in the DNA double helix, contributing to the base pairing rules that maintain the structure of DNA. Cytosine plays a crucial role in encoding genetic information, as it is involved in the formation of codons during protein synthesis.

5 Must Know Facts For Your Next Test

1. Cytosine is classified as a pyrimidine base, which means it has a single-ring structure, distinguishing it from purine bases like adenine and guanine that have a double-ring structure.
2. In DNA, cytosine forms three hydrogen bonds with guanine, making this base pair relatively stable compared to other base pairs.
3. Cytosine can undergo deamination, which converts it to uracil, potentially leading to mutations if not corrected during DNA repair processes.
4. The presence of cytosine in a nucleotide sequence contributes to the genetic code that determines protein synthesis in living organisms.
5. Cytosine methylation is an important epigenetic modification that can regulate gene expression without altering the underlying DNA sequence.

Review Questions

• How does cytosine contribute to the stability and structure of DNA?
  • Cytosine contributes to the stability and structure of DNA through its specific pairing with guanine via three hydrogen bonds. This strong bonding helps to hold the two strands of the DNA double helix together. The correct pairing is essential for maintaining the integrity of the genetic information encoded in the DNA sequence.
• What are the implications of cytosine deamination in terms of genetic mutations?
  • Cytosine deamination converts cytosine into uracil, which can lead to base-pair mismatches during DNA replication if not corrected. This can result in mutations that may affect gene function and contribute to diseases such as cancer. Therefore, repair mechanisms must be in place to detect and fix these changes to preserve genetic stability.
• Analyze the role of cytosine methylation in gene regulation and its significance in epigenetics.
  • Cytosine methylation is a key mechanism in epigenetics that involves adding a methyl group to the cytosine base in DNA. This modification can influence gene expression by silencing genes without changing the underlying DNA sequence. Understanding how cytosine methylation affects gene regulation is crucial for insights into developmental biology and diseases such as cancer, where abnormal methylation patterns can lead to misregulation of critical genes.

Related terms

Nucleotide: The basic building block of nucleic acids, consisting of a nitrogenous base, a sugar, and a phosphate group.

Complementary Base Pairing: The specific pairing between nitrogenous bases in DNA, where cytosine pairs with guanine and adenine pairs with thymine.

DNA Replication: The biological process of producing two identical replicas of DNA from one original DNA molecule, where cytosine plays a key role in ensuring the correct sequence is maintained.