14.1

Cards (16)

  • RNA is a nucleic acid consisting of a long chain of nucleotides that help assemble genetic code
  • RNA uses DNA to make proteins and helps determine an organism's characteristics
  • RNA is single-stranded, contains uracil, and sugar ribose
  • DNA is double-stranded, contains thymine, and deoxyribose
  • messenger RNA (mRNA): carries copies of instructions from the nucleus to ribosomes in the cytoplasm
  • RNA synthesis involves transcription, where a base sequence is copied from DNA to RNA
  • Segments of DNA act as templates to produce complementary RNA molecules
  • RNA polymerase is the enzyme responsible for transcription, binding to DNA, separating it, and using one strand of DNA as a template for a complementary RNA strand
  • This process allows one gene to produce hundreds to thousands of RNA molecules
  • Promoters are where RNA polymerase binds to DNA to start the transcription process
  • Other DNA regions cause transcription to stop when an RNA molecule is completed
  • RNA editing occurs at the pre-mRNA stage, where introns (portions that are cut out and discarded) are removed in the nucleus
  • The remaining pieces, known as exons, are spliced back together to form the final mRNA
  • RNA editing plays a small but important role in evolution
    • Ribosomal RNA (rRNA): proteins are assembled on ribosomes, small organelles with two subunits
    • Transfer RNA (tRNA): carries amino acids to the ribosome during protein assembly and matches them to the coded mRNA message