Cytosine

Definition

Cytosine is one of the four primary nitrogenous bases found in nucleic acids, specifically DNA and RNA. It pairs with guanine through three hydrogen bonds in DNA, playing a critical role in the structure and function of genetic material, as well as the processes of transcription and replication.

5 Must Know Facts For Your Next Test

1. Cytosine is a pyrimidine base, characterized by its single-ring structure, distinguishing it from purines like adenine and guanine which have double-ring structures.
2. In DNA, the presence of cytosine contributes to the overall stability of the double helix due to its ability to form strong hydrogen bonds with guanine.
3. Cytosine can undergo deamination, converting it into uracil in RNA or thymine in DNA, which can lead to mutations if not repaired.
4. The sequence of cytosine and other bases along the DNA strand encodes genetic information essential for the development and functioning of all living organisms.
5. During DNA replication, complementary base pairing ensures that cytosine pairs with guanine, maintaining genetic fidelity as cells divide.

Review Questions

• How does cytosine contribute to the structure and stability of DNA?
  • Cytosine contributes to the structure and stability of DNA by pairing with guanine through three hydrogen bonds. This strong interaction helps maintain the integrity of the double helix structure, which is essential for proper cellular function. The precise pairing ensures that genetic information is accurately copied during replication, which is critical for the continuation of life.
• Discuss the implications of cytosine deamination on genetic fidelity and potential mutations.
  • Cytosine deamination can have significant implications for genetic fidelity. When cytosine is deaminated, it is converted to uracil in RNA or thymine in DNA. If this change goes uncorrected during DNA replication, it can lead to permanent mutations in the genetic code. Such mutations can potentially result in diseases or contribute to evolutionary changes within populations.
• Evaluate the importance of complementary base pairing involving cytosine in the context of both transcription and replication.
  • Complementary base pairing involving cytosine is crucial for both transcription and replication processes. During transcription, cytosine pairs with guanine on the template strand to ensure accurate messenger RNA synthesis. In replication, this pairing guarantees that each new DNA molecule retains the correct sequence of nucleotides. This fidelity is vital for maintaining genetic information across generations and ensuring proper cellular function.

Related terms

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

Complementary Base Pairing: The specific pairing of nitrogenous bases in nucleic acids, where cytosine pairs with guanine, ensuring accurate replication and transcription.

RNA:

Ribonucleic acid, a nucleic acid that plays essential roles in coding, decoding, regulation, and expression of genes, containing cytosine as one of its bases.