RNA and Nucleic Acid Chemistry

• RNA serves as the genetic material in some viruses. Some viruses have an RNA core rather than a DNA core
• Experiments with tobacco mosaic virus (1956) demonstrated that RNA serves as the genetic material for these viruses
• Replication of the viral RNA is dependent on RNA replicase
• Retroviruses replicate in an unusual way. RNA is a template for synthesis of a complementary DNA by the RNA-dependent DNA polymerase called reverse transcriptase. This DNA can be incorporated into the host cell genome; when transcribed copies of the original retroviral RNA chromosomes are also produced
• Knowledge of nucleic acid chemistry is essential to the understanding of DNA structure
• Nucleotides are the building blocks of DNA

  • Nitrogenous base
  • Pentose sugar
  • Phosphate group
• Nitrogenous bases

  • Purines (adenine and guanine)
  • Pyrimidines (cytosine, thymine, uracil)
• DNA and RNA both have A, C, and G. DNA has T, RNA has U
• RNA has ribose for sugar, DNA has deoxyribose
• A nucleoside contains the nitrogenous base and the pentose sugar

  A nucleotide is a nucleoside with a phosphate group added
• The C-5’ position is the location of the phosphate group on a nucleotide
• Nucleotides can have 1, 2, or 3 phosphate groups and are called NMPs, NDPs, and NTPs.
• Nucleotides are linked by a phosphodiester bond between the phosphate group at the C-5’ position and the OH groups on the C-3’ position