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• The Central Dogma


  The fundamental principle of molecular biology describing the flow of genetic information within a biological system

  
• DNA


  • The genetic material within the nucleus
  • Replication creates new copies of DNA
  • Transcription creates an RNA using DNA information
  • Translation creates a protein using RNA information

  
• Replication


  1. DNA Replication is semi-conservative

  2. Each newly synthesized molecule contains 1 "parent template" strand and 1 new "daughter" strand

  
• RNA


  • An important type of nucleic acid that plays several roles in the production of protein
  • Necessary to carry the instructions of the DNA out of the nucleus and to the ribosomes

  
• Types of RNA


  • mRNA (messenger RNA)
  • tRNA (transfer RNA)
  • rRNA (ribosomal RNA)
  • snRNA (small nuclear RNA)

  
• Transcription


  1. DNA is used as a template for creation of RNA using the RNA polymerase

  2. RNA polymerase reads the nucleotides on the template strand from 3' to 5' and creates an RNA molecule in a 5' to 3' direction that looks like the coding strand

  3. The new RNA molecule is formed by incorporating nucleotides that are complementary to the template strand

  
• Initiation of Transcription


  • Transcription begins at the 3' end of the gene in a region called the promoter
  • The promoter recruits TATA protein, a DNA binding protein, which in turn recruits other proteins

  
• Transcription Process


  RNA synthesis involves separation of the DNA strands and synthesis of an RNA molecule in the 5' to 3' direction by RNA polymerase, using one of the DNA strands as a template

  
• Complete Transcription of an RNA Molecule

  Transcription begins at the promoter, proceeds through the coding region, and ends at the terminator

  
• Codon


  • A triplet of adjacent nucleotides in the messenger RNA chain that codes for a specific amino acid in the synthesis of a protein molecule
  • Each codon corresponds to a single amino acid (or stop signal), and the full set of codons is called the genetic code

  
• All organisms use the same 20 amino acids and each codon specifies a particular amino acid
• Translation


  The process of reading the RNA sequence of an mRNA and creating the amino acid sequence of a protein

  
• The "Players" in Translation

  • Messenger RNA (mRNA)
  • Ribosomes
  • Transfer RNA (tRNA)
  • Amino Acids

  
• mRNA


  • Synthesized in transcription
  • Composed of Codons
  • Codons are 3-base sequences of mRNA

  
• Transfer RNA


  • In the cytoplasm, a ribosome attaches to the mRNA and translates its message into a polypeptide
  • The process is aided by transfer RNAs

  
• Ribosomes


  • Made of rRNA and protein
  • 2 subunits (large and small) form a 3D groove

  
• Amino Acids


  • There are 20 amino acids, each with a basic structure
  • Amino acids are held together by peptide bonds
• Translation has 3 steps

  1. Initiation

  2. Elongation

  3. Termination
• Initiation


  mRNA, a specific tRNA, and the ribosome subunits assemble during initiation

  
• Elongation


  The ribosome lengthens the polypeptide (amino acid chain) by adding new amino acids to the growing chain
• Termination


  The ribosome reaches the stop codon and the elements disassemble
• The Genetic Code is a triplet code where each codon specifies a particular amino acid
• Mutation


  • Any change in the nucleotide sequence of DNA
  • It may involve large sections of chromosomes or single base pairs
  • Mutations can change the reading frame of a gene transcript
• Types of Mutations


  • Substitution
  • Insertion/Deletions
• Deletion or insertion mutations are most disruptive because they change the reading frame, causing a frame shift
• Substitution mutations have varied impact on amino acid sequences
• What causes Mutations?


  • Errors in DNA Replication
  • Errors in chromosome crossover in meiosis
  • Mutagens (UV Radiation, X-Rays, Chemicals like DDT)
• Recent research paper (2015) showed a novel relationship between genotype and phenotype using SCTG (Single-cell transcriptogenomics)