Bio

• Nucleotides


  Building blocks of nucleic acids
• Nucleotide


  Composed of a phosphate group, a sugar portion, and an N-base
• Purines, pyrimidines

  _____ (adenine, guanine) and _____(cytosine, thymine, uracil)
• DNA base pairing


  A pairs with T, G pairs with C
• DNA structure


  Double stranded
• RNA structure


  Single stranded with uracil instead of thymine
• DNA function


  Repository of genetic information, sequences of bases encode the blueprint of life processes
• RNA function


  Information in the form of base sequence is transformed (transcribed) into mRNA, tRNA and rRNA. DNA is the template copied into RNA by base pairing, G with C; A with U.
• Protein structural levels


  • Primary - sequence of amino acids
  • Secondary - helix or pleated sheet
  • Tertiary - coiling of polypeptide
  • Quaternary - association of two or more polypeptides
• Interphase


  1. Cell grows and makes a copy of DNA

  2. G1 (Gap/Growth 1) - cell grows in size, copies organelles

  3. S (synthesis) - Copies DNA, Copies Centrosome

  4. G2 (Gap/Growth 2) - cell grows more, reorganizes to prepare for Mitosis
• DNA


  Molecule that carries the genetic information of an organism
• DNA characteristics


  • Replication
  • Storage of information
  • Expression of information
  • Genetic variation
• DNA structure


  Double-stranded molecule consisting of long chains of monomers called nucleotides
• Nucleotide


  Composed of pentose sugar, phosphate group, and nitrogenous base
• Phosphodiester bonds


  Bonds that link the nucleotides together
• DNA structure


  Right-handed double helix, antiparallel chains
• Pentose sugar


  Monosaccharide composed of five carbon atoms, deoxyribose in DNA, ribose in RNA
• Phosphate group


  Contains a phosphorus atom bonded to four oxygen atoms, linked to the pentose sugar on Carbon 5'
• Nitrogenous base


  Molecule containing nitrogen with chemical properties of a base, purines and pyrimidines
• Nucleoside


  Molecule composed of pentose sugar and nitrogenous base
• Nucleotide


  Nucleoside with a phosphate group added
• DNA base pairing


  Adenine (A) pairs with thymine (T) with two hydrogen bonds, cytosine (C) pairs with guanine (G) with three hydrogen bonds
• RNA


  Single-stranded molecule, ribose sugar, uracil replaces thymine
• Major classes of RNA

  • Messenger RNA (mRNA)
  • Transfer RNA (tRNA)
  • Ribosomal RNA (rRNA)
• mRNA


  Carries genetic information from DNA to ribosome
• tRNA


  Carries amino acids to ribosome during translation, has specific anticodon
• rRNA


  Structural components of ribosomes
• DNA replication


  1. Copied from parent cell to daughter cell

  2. Required in mitotic cell division and meiosis
• Enzymes/substances involved in DNA replication

  • DNA Helicase
  • DNA Gyrase
  • RNA Primer
  • DNA Polymerase
  • DNA Ligase
  • Single-Stranded Binding Proteins
• DNA Helicase


  Unwinds the double stranded DNA during replication
• DNA Gyrase


  Relaxes DNA during supercoiling
• RNA Primer


  Short nucleotide sequence that initiates DNA replication
• DNA Polymerase


  Assembles new DNA nucleotides using parent strand as template, removes and replaces incorrect nucleotides
• DNA Ligase


  Joins DNA fragments together, catalyzes formation of phosphodiester bonds
• Single-Stranded Binding Proteins


  Bind and stabilize single-stranded regions of DNA during replication
• DNA replication steps


  1. DNA helicase unwinds double-stranded DNA, creating replication fork

  2. Leading strand - continuous DNA synthesis 3' to 5'

  3. Lagging strand - discontinuous DNA synthesis 5' to 3', Okazaki fragments

  4. DNA gyrase relaxes supercoiling, RNA primer initiates replication

  5. DNA polymerase adds nucleotides, removes primers

  6. DNA ligase joins Okazaki fragments

  7. DNA polymerase proofreads and replaces incorrect nucleotides
• Types of DNA replication

  • Conservative replication
  • Semiconservative replication
  • Dispersive replication
• Genetic code


  Codon in mRNA is either translated into an amino acid or serves as a start/stop signal
• Transcription


  1. Transfer of information from DNA to complementary mRNA sequence

  2. Initiation - RNA polymerase attaches to promoter

  3. Elongation - Ribonucleotides inserted and linked by phosphodiester bonds

  4. Termination - Termination factors cause transcript to form hairpin structure
• RNA Polymerase


  Enzyme that catalyzes formation of RNA polynucleotide strand using DNA as template