Structure and Function of Nucleic Acids

Structure and Function of Nucleic Acids

• DNA and RNA are polymers of nucleotide units, consisting of four kinds of ribonucleotide units linked together through covalent bonds.

Components of DNA and RNA

• Each nucleotide unit is composed of:
  • a nitrogenous base
  • a pentose sugar
  • a phosphate group

Importance of DNA Packing into Chromosomes

• Chromosome is a compact form of DNA that readily fits inside the cell.
• Packing DNA into chromosomes:
  • protects DNA from damage
  • allows for efficient transmission to daughter cells during cell division
  • confers an overall organization to each molecule of DNA, facilitating gene expression and recombination.

Functions of DNA

• Carries genetic information
• Acts as a template strand in replication and transcription
• Gene: the minimum functional unit in DNA
• Genome: the total genes in a living cell or living beings

Structures and Functions of RNA

• Conformational variability of RNA is important for its diverse roles in the cell.
• Types of RNA:
  • mRNA (messenger RNA): carries genetic information from DNA to translate into protein
  • tRNA (transfer RNA): transports amino acids to ribosomes for protein synthesis
  • rRNA (ribosomal RNA): components of ribosomes
  • hnRNA (Heterogeneous nuclear RNA)
  • snRNA (small nuclear RNA)

RNA Structure

• RNA molecules are largely single-stranded but have double-stranded regions.

Messenger RNA (mRNA)

• Function: carries genetic information from DNA for protein synthesis
• Comprises only about 5% of the RNA in the cell
• Composition: varies considerably in size (500-6000 bases in E. coli)