Final Exam Bio 1200

• Silent mutation


  Does not alter the amino acid sequence due to degeneracy of genetic code
• Missense mutation


  Changes a single amino acid in a polypeptide, may not alter function if substituted amino acid is similar in chemistry to original
• Missense mutation


  • Sickle-cell disease
• Nonsense mutation


  Change from a normal codon to a stop codon, produces a truncated polypeptide
• Frameshift mutation


  Addition or deletion of nucleotides/bases (excluding multiples of 3), completely different amino acid sequence downstream from mutation
• Germ-line mutation


  Mutation can occur in sperm or egg cell, or in gamete progenitor cells, passed to offspring
• Somatic mutation


  Occurs in all other body cells, can occur early or late in development, gives a genetic mosaic with patches of mutant tissue
• Spontaneous mutation


  Free radicals produced from abnormalities in biological processes, rates vary species to species and gene to gene, background mutation rate approximately 1 mutation / million genes
• Induced mutation


  Caused by environmental agents, higher rate than spontaneous mutations
• Mutagen


  Chemical or physical agent that alters DNA
• Chemical mutagen


  Alters the structure of DNA, e.g. Nitrous Oxide
• Effect of nitrous oxide

  Change cytosine into Uracil, NH2 is being changed to O, C pairs with G, U pairs with A
• Ionizing radiation


  • Xrays and Gamma Rays
• Non-ionizing radiation


  Has less energy and can only penetrate the surface, UV rays can cause formation of thymine dimers, causing gaps or incorporation of incorrect bases
• Types of DNA repair

  • Direct repair
  • Nucleotide excision repair
  • Methyl-directed mismatch repair
• Diseases associated with faulty DNA repair

  • Xeroderma pigmentosum (XP)
  • Cockayne's syndrome (CS)
  • PIBIDS
• Progression of cancer


  Starts from one cell, followed by overgrowth leading to formation of tumor, cells detach from the tumor (malignant tumor) and migrate somewhere else and develop into tumors (metastasis)
• Tumor


  An overgrowth of cells with no useful purpose, may begin as benign or pre-cancerous, may become malignant - extreme overgrowth of cells
• Metastasis


  When cells migrate to other parts of the body
• Checkpoint proteins


  Check the integrity of the genome and prevent a cell from progressing past a certain point in the cell cycle
• Cyclins and cyclin-dependent protein kinases (cdks)

  Responsible for advancing a cell through the four phases of the cell cycle, formation of activated cyclin/cdk complexes can be stopped by checkpoint proteins
• p53


  A transcription factor that acts as a sensor of DNA damage, can promote DNA repair, prevent the progression through the cell cycle, and promote apoptosis
• Retinoblastoma (RB)


  A negative regulator of growth that stops cell division.
• Examples of Ionizing Radiation 


  X-Rays and Gamma Rays