Nucleotide

Definition

A nucleotide is the basic building block of nucleic acids, which include DNA and RNA. Each nucleotide consists of three components: a nitrogenous base, a five-carbon sugar (deoxyribose in DNA and ribose in RNA), and one or more phosphate groups. Nucleotides are essential for the structure of DNA, where they form the genetic code through sequences that encode information for living organisms.

5 Must Know Facts For Your Next Test

1. Nucleotides link together through phosphodiester bonds to form long chains known as polynucleotides, which are essential for creating DNA and RNA strands.
2. The sequence of nucleotides in DNA determines the genetic information and is often referred to as the genetic code.
3. Each nucleotide contains a unique nitrogenous base, which can be adenine (A), thymine (T), cytosine (C), or guanine (G) in DNA.
4. In RNA, uracil (U) replaces thymine as one of the nitrogenous bases, resulting in the base pairing of adenine with uracil.
5. Nucleotides also play a critical role in cellular metabolism, as some serve as energy carriers, such as adenosine triphosphate (ATP).

Review Questions

• How do nucleotides contribute to the overall structure of DNA?
  • Nucleotides contribute to the structure of DNA by linking together through phosphodiester bonds to form long chains known as polynucleotides. Each nucleotide consists of a nitrogenous base, a sugar, and phosphate groups, which help create the backbone of the DNA strand. The specific sequence of these nucleotides encodes genetic information and enables the formation of the double helix structure through complementary base pairing.
• Discuss the differences between DNA and RNA nucleotides and their functional implications.
  • DNA nucleotides contain deoxyribose sugar and use thymine as one of their nitrogenous bases, while RNA nucleotides contain ribose sugar and use uracil instead of thymine. These differences affect their structure and function; for instance, DNA is typically double-stranded and more stable, making it ideal for long-term storage of genetic information. In contrast, RNA is usually single-stranded and plays a key role in protein synthesis and gene expression, which requires more flexibility.
• Evaluate the importance of nucleotide sequences in determining genetic traits and how mutations can affect these sequences.
  • Nucleotide sequences are crucial for determining genetic traits since they encode instructions for synthesizing proteins that affect an organism's characteristics. Changes or mutations in these sequences can lead to alterations in protein function or expression, potentially resulting in various phenotypes or diseases. For example, a single nucleotide mutation could lead to a change in amino acid sequence during protein synthesis, impacting enzyme activity or structural integrity, which could have significant consequences on an organism's health or development.

Related terms

DNA:

Deoxyribonucleic acid, the molecule that carries genetic instructions for the development, functioning, growth, and reproduction of all known living organisms.

RNA: Ribonucleic acid, a molecule involved in protein synthesis and the transmission of genetic information from DNA to proteins.

Complementary base pairing: The specific pairing between nitrogenous bases in DNA (adenine with thymine, and cytosine with guanine) that helps to stabilize the double helix structure.