Test 7

• Transcription: DNA-directed synthesis of RNA
• Translation: Synthesis of polypeptides(proteins) from RNA
• Codon: block of 3 DNA nucleotides
• Introns: non-coding sequences
• Exons: sequences that will be translated
• Transcription: DNA-directed synthesis of RNA

  DNA -> RNA

  Translation: Synthesis of polypeptides (proteins) from RNA

  RNA -> protein
• The Central Dogma

  • Genetic information flows from
  • DNA -> RNA -> protein
  • Transcription: DNA -> RNA
  • Translation: RNA -> protein
  • Retroviruses violate this order
  • Use reverse transcriptase to convert RNA genome into DNA
• Transcription

  • Transcription: DNA-directed synthesis of RNA, DNA -> RNA
  • Only template strand of DNA is used
  • Uses 3 different RNA polymerases
  • RNA polymerase I: transcribes rRNA
  • RNA polymerase II: transcribes mRNA and some snRNA
  • RNA polymerase III: transcribes tRNA and other small RNAs
  • Each RNA recognizes its own type of promoter
• Translation

  • Translation: synthesis of polypeptides, RNA -> Proteins
  • Takes place at ribosome
  • Requires several kinds of RNA
• RNA

  • All synthesized from DNA template by transcription
  • Many different kinds;
  • messenger RNA (mRNA),
  • ribosomal (rRNA),
  • transfer (tRNA)
• Codons

  • Codon: block of 3 DNA nucleotides
  • Spaced codons: codon sequence in a gene is punctuated
  • Unspaced codons: codons that are adjacent to each other
• Mutations

  • Point mutations alter a single base
  • Base substitution – substitute one base for another
  • Silent mutation – same amino acid inserted
  • Missense mutation – changes amino acid inserted
  • Transitions, Transversions
  • Nonsense mutations – changed to stop codon
• Transcription Complex

  • Nearly every eukaryotic gene represents a unique case
  • Great flexibility to respond to many signals
  • Virtually all genes that are transcribed by RNA polymerase II need the same suite of general factors to assemble an initiation complex
• 1. DNA Replication

  Start: 1 DNA strand

  End: 2 DNA strands

  2. Transcription

  Start: DNA

  End: RNA transcript

  3. Translation

  Start: RNA

  End: An amino acid sequence or a polypeptide.
• Proteins:

  • build and repair muscles and bones and to make hormones and enzymes
  • Made up of amino acids
  • Can be used as an energy source
• Operon: groups functionally related genes
• RNA polymerase I: transcribes rRNA

  RNA polymerase II: transcribes mRNA and some snRNA

  RNA polymerase III: transcribes tRNA and other small RNAs
• Transcription bubble contains

  • RNA polymerase
  • DNA template
  • Growing RNA transcript
• Operon: groups functionally related genes
• Eukaryotic Pre-mRNA Splicing

  • Introns: non-coding sequences
  • Exons: sequences that will be translated
  • Small ribonucleoprotein particles (snRNPs) recognize intron-exon
• Base substitution – substitute one base for another
• Silent mutation – same amino acid inserted
• Missense mutation – changes amino acid inserted

  • Transitions
  • Transversions
• Nonsense mutations – changed to stop codon
• • Prokaryotes regulate gene expression in response to environment
  • Eukaryotes regulate gene expression to maintain homeostasis
  • Regulatory proteins bind to DNA
  • May block or stimulate transcription
• Glucose Repression

  • Preferential use of glucose in the presence of other sugars
  • Inducer exclusion – presence of glucose inhibits the transport of lactose into the cell
• Polymerase Chain Reaction (PCR)

  Each PCR cycle involves three steps:

  1. Denaturation (high temperature)
  2. Annealing of primers (low temperature)
  3. DNA synthesis (intermediate temperature)
• Ways to edit geno

  1. TALE (transcription activator-like effector) proteins

  • Allows you to deactivate troublesome genes

  2) CRISPR/Cas9 system

  • Can either active or repress gene expression/find the location of genes
• Genetically modified organisms (GMOs)
• Transgene: gene from another species
• Codon: block of 3 DNA nucleotides
• Transcription: DNA-directed synthesis of RNA, DNA  RNA

  • Only template strand of DNA is used
  • T (thymine) in DNA is replaced by U (uracil) in RNA
• DNA Methylation: used to be important in the development of cancer, but now it is thought to be a marker of aging
• Recombinant DNA: a single DNA molecule made from two different sources
• Restriction Endonucleases = Ability to cut DNA into specific fragments (so you can research just one part of DNA)
• DNA Ligase = can essentially insert DNA