DNA and RNA

• DNA stands for Deoxyribonucleic Acid
• DNA is a biomolecule
• Monomer of DNA


  Nucleotide
• Components of a nucleotide

  • Sugar
  • Phosphate group
  • Nitrogenous base
• Sugar found in DNA is Deoxyribose
• The sides of the DNA ladder are made of sugar-phosphate backbones
• The rungs of the DNA ladder are made of paired nitrogenous bases
• Covalent bonds in DNA

  Found in the sugar-phosphate backbone
• Hydrogen bonds in DNA

  Found between paired nitrogenous bases
• Covalent bonds are strong, while hydrogen bonds are weak
• Shape of DNA


  Double helix
• Antiparallel means the two strands of DNA run in opposite directions
• Chargaff’s Rule states that in DNA, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine
• DNA codes for genetic information
• DNA replication is the process of making an identical copy of DNA. It happens to ensure genetic continuity before cell division
• Molecules responsible for DNA replication are DNA polymerase, helicase, primase, and ligase
• Functions of the 4 enzymes in replication are unwinding the DNA, synthesizing RNA primers, synthesizing new DNA strands, and joining fragments
• Leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously in Okazaki fragments
• DNA replication is semiconservative because each new DNA molecule consists of one parent strand and one newly synthesized strand
• Central Dogma of biology states that DNA is transcribed into RNA, which is then translated into proteins
• DNA and RNA are alike as nucleic acids but differ in sugar composition (deoxyribose in DNA, ribose in RNA) and the presence of thymine in DNA and uracil in RNA
• First step of protein synthesis is transcription, occurring in the nucleus, where RNA polymerase synthesizes mRNA from DNA
• Second step of protein synthesis is translation, occurring in the cytoplasm, where mRNA is decoded by ribosomes to synthesize proteins
• Codon is a three-nucleotide sequence on mRNA, while an anticodon is a complementary three-nucleotide sequence on tRNA
• Codon codes for a specific amino acid
• Mutation is a change in the DNA sequence
• Types of gene mutations

  • Insertion
  • Deletion
  • Substitution
• Frameshift mutations are insertions and deletions, affecting the reading frame and leading to significant changes in the translated amino acid sequence
• Silent mutation does not change the amino acid, nonsense mutation creates a premature stop codon, and missense mutation changes one amino acid to another
• Mutagen is a substance that causes mutations. Examples include UV radiation and certain chemicals
• Main causes of mutations are environmental factors (mutagens) and errors during DNA replication
• Mutations can be beneficial by introducing genetic diversity or harmful by causing diseases
• Biotechnologies


  • Gel electrophoresis
  • PCR (Polymerase Chain Reaction)
  • Genetically modified organisms
  • Cloning
  • Gene therapy
• RNA primase: Builds an RNA primer on leading and lagging strands

  DNA polymerase: Adds daughter nucleotides on the parent strands

  DNA ligase: Joins Okazaki fragments to form a continuous strand

  DNA helicase: Unwinds the double helix by breaking hydrogen bonds
• What are the steps of replication? the opening of the double helix and separation of the DNA strands, the priming of the template strand, and the assembly of the new DNA segment
• What's the process of transcription? RNA Polymerase binds to the promoter and starts to unwind the DNA exposing the nucleotides. RNA polymerase reads the DNA and adds complementary nucleotides. RNA polymerase continues until the terminator
• Translation is important because it converts mRNA into protein using ribosomes.
• Types of gene mutations

  • Silent mutation
  • Nonsense mutation
  • Missense mutation
• Silent mutation


  A type of gene mutation where the change in DNA sequence does not affect the final protein that is produced