FINALS

• DNA


  DeoxyriboNucleic Acid, the genetic material
• Information stored in DNA

  • The basis of inheritance
  • Distinguishes living things from nonliving things
• Genes


  Various units that govern living thing's characteristics at the genetic level
• Genes


  Segments of your DNA, which give you physical characteristics that make you unique
• Nucleotides


  Genes themselves contain their information as a specific sequence of nucleotides found in DNA molecules
• Bases in DNA molecules

  • Guanine (G)
  • Adenine (A)
  • Thymine (T)
  • Cytosine (C)
• Nucleotide


  Each base is attached to a phosphate group and a deoxyribose sugar to form a nucleotide. The only thing that makes one nucleotide different from another is which nitrogenous base it contains
• DNA strand


  A nucleic acid strand is inherently directional, and the "5 prime end" has a free hydroxyl (or phosphate) on a 5' carbon and the "3 prime end" has a free hydroxyl (or phosphate) on a 3' carbon
• Central Dogma of Molecular Biology


  The detailed residue-by-residue transfer of sequential information. It states that such information cannot be transferred back from protein to either protein or nucleic acid
• DNA


  Information storage
• Protein


  Function unit, such as enzyme
• Gene


  Instructions needed to make protein
• Complementary DNA (cDNA)


  DNA obtained from reverse transcription
• Making copies of a specific genetic sequence

  Uses an enzyme called reverse transcriptase to change a specific piece of RNA into a matching piece of DNA
• RNA (RiboNucleic Acid)


  Single-stranded polynucleotide
• Bases in RNA


  • A
  • G
  • C
  • U (Uracil), instead of T
• Transcription (simplified)


  A → A, G →G, C → C, T → U
• DNA Replication


  1. Replication Fork Formation

  2. Primer Binding

  3. Elongation

  4. Termination
• Helicase


  Unwinds parental double helix
• Ligase


  Joins Okazaki fragments and seals other breaks in sugar- phosphate backbone
• DNA Polymerase


  Binds nucleotides to form new strands
• RNA Primer


  Short segment of nucleic acid made up of a single-stranded RNA molecule. Required for DNA replication to initiate DNA synthesis
• Steps of Replication


  1. The 2 nucleotide strands separate at base pairs. They unzip like a zipper using DNA Helicase (enzyme)

  2. RNA primers start the addition of new nucleotides

  3. DNA replication takes place at a Y-shaped structure called a replication fork. A self-correcting DNA polymerase enzyme catalyzes nucleotide polymerization, copying a DNA template strand with remarkable fidelity
• Steps of Replication


  1. Elongation is unidirectional, that is, DNA is always polymerized only in the 5′ to 3′ direction. One strand (the template 3'→5') it is continuous, hence called continuous replication while on the other strand (the template 5'→3') it is discontinuous replication. They occur as fragments called Okazaki fragments. Replication moves in only ONE direction. So, small DNA segments called Okazaki fragments are made on the other strand. The enzyme called DNA ligase joins them later

  2. The terminator is a region of DNA that that codes for the Rho binding site in the mRNA and the actual transcription stop point

  3. Each new DNA molecule has 1 nucleotide strand from the original DNA molecule and 1 nucleotide strand made from free nucleotides in the nucleus
• Semi-conservative replication


  Each new DNA molecule contains one old strand & one new strand
• Transcription


  1. Double stranded DNA must be TRANSCRIBED into Single stranded RNA

  2. RNA contains coded information for making proteins

  3. Transcription proceeds in the 5' to 3' direction (the old polymer is read in the 3' to 5' direction and the new, complementary fragments are generated in the 5' to 3' direction)
• 3 Types of RNA made from DNA

  • mRNA →"messenger" (made from DNA in nucleus…travels out of nucleus and finds a ribosome)
  • tRNA →"transfer" (brings amino acids to the ribosomes; found in cytoplasm)
  • rRNA → "ribosomal" (part of the ribosome; this is where proteins are made)
• Transcription


  1. RNA molecules are produced by copying part of a nucleotide sequence of DNA into a complementary sequence in RNA. This process is called transcription

  2. Transcription requires the enzyme RNA polymerase
• Transcription Steps


  1. RNA polymerase binds to the promoter site (TATA box) (start) on the DNA

  2. RNA polymerase adds RNA nucleotides complimentary to the DNA strand

  3. mRNA building is complete when the RNA polymerase reaches a Termination (stop) site on the DNA

  4. This strand of mRNA is EDITED before leaving the nucleus & carrying the code into the cytoplasm
• DNA never leaves the nucleus
• hnRNA (heterogeneous nuclear RNA)


  The collective term for the unprocessed mRNA (pre-mRNA) molecules in the nucleus. It is largely comprised of the pre-mRNA molecules that require extensive processing to become mature mRNA molecules
• hnRNA processing to form mRNA

  1. Capping: Addition of methyl guanosine triphosphate at 5-end

  2. Tailing: Addition of 200-300 adenylate residues at 3-end

  3. Splicing: Removal of introns and joining of exons
• Exons


  Carry information for protein synthesis
• Introns


  Interrupting sequences that do not code for any protein but are found between exons
• mRNA Editing


  Introns are cut out before leaving the nucleus and Exons are left. The shortened piece of mRNA leaves the nucleus and gets translated into proteins
• Translation


  The mRNA codes for certain amino acids. Strings of amino acids are proteins
• Translation Steps


  1. Messenger RNA is transcribed in the nucleus, and then enters the cytoplasm where it attaches to a ribosome (to begin translation)

  2. Translation begins when an mRNA molecule attaches to a ribosome

  3. As each codon (group of 3 nucleotides)of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome by tRNA

  4. In the ribosome, amino acids are transferred to the growing polypeptide chain by the action of the tRNA (elongation)

  5. When the "STOP" codon is reached the mRNA uncouples from the ribosome
• tRNA


  Each tRNA molecule carries only one kind of amino acid (as determined by the anti-codon). In addition to an amino acid, each tRNA molecule has three unpaired bases called the anticodon, which are complementary to one mRNA codon
• Peptides and Proteins


  • mRNA → Sequence of amino acids connected by peptide bond
  • Peptide: < 30 – 50 amino acids
  • Protein: longer peptide
• Genetic Code


  The "language" of mRNA instructions, written using four "letters" (the bases: A, U, C, and G)