Genetics Final Review

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  1. Mutation
    Heritable changes in genetic material

    DNA sequence changes

    Chromosomal alterations
  2. Mutation rate
    The number of events that produce mutated alleles per locus per generation

    Average: 1 mutation per 1 million bp

    Rates vary: gene-gene, with exposure
  3. Reasons for mutational variation by gene
    Size of gene-increase mutation

    repeats within gene - increase mutation

    # of cytosines in gene - if alot chance of spontaneous mutation sequence
  4. Physical Mutagens: UV
    Nonionizing radiation

    absorbed directly by DNA

    thymidine dimers - deletion occurs during replication
  5. Physical Mutagens:ionizing radiation
    X-rays (direct hit)

    Free radicals/electrons (indirect hit)`
  6. Physical Mutagens:Radiation exposure
    rem=radiation equivalent in man

    millirem= 1/1000 rem
  7. Chemical Mutagens:Base analogs
    structure resembles nucleotides

    may incorporate into DNA

    • may lead to wrong base pairing
    • Ex: 5-BU
  8. Chemical Mutagens:Base modifiers
    Chemicals that interact with bases

    change one base into another

    Ex: Nitrous Acids/Nitrates (processed meats)

    CG ->UA -> AT
  9. Chemical Mutagens: DNA intercalating chemicals
    DNA binders

    insert into DNA double helix

    distorts the helix

    leads to insertions/deletions

    mutations occur during replication

    Ex:ethidium bromide
  10. Relationship between mutagens and carcinogens
  11. Point Mutations
    change of 1 or 2 nucleotides in the DNA of a gene
  12. Base pair substitutions
    substituting 1 base for another
  13. Frameshift Mutations
    1-2 base deletion/insertion

    severe to a protein


    alters the reading frame

    protein is altered: very different, truncated, or runs on
  14. Base pair substitutions: Silent mutation
    phenotypically silent

    nucleotide change but no amino acid change in making protein
  15. Base pair substitutions: Nonsense Mutations
    Nucleotide change

    leads to a premature stop codon

    depending on how early mutation occurs will determine if truncated, reduced function, or nonfunctional protein will result
  16. Base pair substitutions: Missense Mutations
    nucleotide change

    putting wrong amino acid in protein

    leads to amino acid change

    may have significant consequences/may no neutral and have no consequences

    Ex: sickle cell disease
  17. DNA replication repair: DNA polymerase proofreading
    1st line of  defense

    In S phase
  18. DNA replication repair:DNA mismatch repair
    Mismatched bases missed by DNA polymerase

    MUT proteins - scan for these replication mismatches

    They are cut out and fixed in S phase
  19. DNA replication repair:DNA excision repair
    Existing DNA duplex is scanned for mutations (usually at G1/S ckpt)

    Damage is cut and fixed

    Many different repair enzymes

    Occurs in G2 phase`
  20. Difficulties in determining mutation rate in human pedigrees
    Its difficult because of criteria:

    single gene trait

    dominant gene

    gene must be completely penetrant

    must be certain of paternity

    no environmental triggers
  21. What is transcription and where does it occur
    It copies a gene's DNA sequence into mRNA sequence and occurs in the nucleus
  22. what are the three stages of transcription
    • transcription initiation
    • transcription elongation
    • transcription termination
  23. Describe transcription initiation
    • transcription factors bind to DNA at the TATA box
    • RNA polymerase II binds with transcription factors
    • Polymerase moves along DNA toward gene
    • transcription bubble forms
    • RNA is made de novo off of DNA template
  24. Describe transcription elongation
    • RNA polymerase moves along DNA template
    • transcription bubble moves
    • Complementary base pairs continue
    • Ribonucleotides join (phosphodiester linkage)
    • RNA is made 5' to 3' (adding on the 3' end)
  25. Describe transcription termination
    • Polymerase hits termination (stop) sequence
    • Polymerase falls off DNA template strand
    • mRNA is released (called pre-mRNA)
  26. Whats mRNA processing.....explain?
    • Its the intermediate step between transcription and translation where transcript modifications occur. 
    • Such as: 5' cap is added, RNA splicing, 3' poly A tail is added, and prepares pre-mRNA before it leaves the nucleus
  27. Whats translation and wheres it occur?
    Conversion of information encoded in the nucleotide sequence of an mRNA molecule into the linear sequence of amino acids that code for a protien and it occurs in the cytoplasm
  28. What are the three stages of translation?
    • translation initiation
    • translation elongation
    • translation termination
  29. Describe translation initiation
    • mRNA binds to small ribosome unit
    • start codon of mRNA is recognized (AUG)
    • tRNA anticodon (UAC) binds to start codon
    • *methionine is 1st amino acid 
    • large ribosome subunit attaches
  30. Describe translation elongation
    • intact ribosome reads mRNA 5' to 3'
    • moves one codon at a time
    • new tRNA binds to codon
    • adjacent amino acids are joined by peptide bond (covalent bond)
    • first tRNA releases its amino acid and leaves
    • process continues
  31. Describe translation termination
    • stop codon is reached
    • ribosome subunits come apart
    • mRNA is released 
    • polypeptide (protein) is released
  32. Explain genetic code
    • Universal
    • triplet "codon" sequence
    • non-overlapping 
    • degenerate- alot of redundancy
    • genetic code table
    • 4 bases(A-U/G-C) arranged in 3's (codon) 64 possibilities to get to the 20 amino acids
  33. Name the three types of RNA in a cell
    • mRNA-messenger RNA
    • tRNA-transfer RNA
    • rRNA-ribosomal RNA
  34. Describe mRNA role in the cell?
    single-stranded complementary copy of the amino acid coding nucleotide sequence of a gene
  35. Describe tRNA role in the cell?
    • (single-strand folds on itself)
    • small RNA molecule that contains a binding site for a specific type of amino acid & has three base segment known as a anticodon that recognizes a specific base sequence in mRNA
  36. Describe rRNA role in the cell?
    RNA molecules that form part of the ribosome
  37. Name the protein structures
    • primary
    • secondary-(folding)=alpa helix (spiral) / pleated sheets (wavy)
    • tertiary-most proteins stop here
    • quaternary- two or more proteins (ex: hemoglobin)
  38. Chaperone proteins
    assist in normal folding
  39. Prions
    type of chaperone protein that causes abnormal folding of proteins (ex: mad cow disease from prions)
  40. Post translational modifications
    addition of carbohydrates, lipids, and phosphates which lead to many different functional proteins
  41. Proteolysis
    big protein cut to small specific portions for specific tasks
  42. Protein interactions
    • when 2 proteins get together and do something they wouldn't do on their own. 
    • 22-23,000 genes can turn into 2-300,000 genes
  43. Name the three types of cancer
    • oncogenes 
    • tumor suppression genes
    • DNA repair genes (mutator genes)
  44. 4 most common sites of cancer in humans
    breast lung prostate colon
  45. 3 reasons we see different prognosis for different types of cancer
    • aggressive nature of the cancer: ex: pancreatic, lung cancer
    • amendable to early detection:  can we catch it early ,not all amendable (breast, prostate)
    • adequate therapeutic treatments:  some cancers yes some no
  46. Why is cancer primarily a disease of older age?
    • simple probability
    • longer exposure period to mutagens/carcinogens
    • immune system decline
  47. Explain this statement, "Cancer is a genetic disease"
    Accumulation of alterations in somatic cell genes lead to the development of cancer...cancer is therefore a genetic disease at the cellular level.
  48. Explain the process of tumorigensis.... changes in tissue, changes in the cell
    • tumorigenesis is how a normal cell becomes a cancer cell
    • Its a multi process step
    • Each step involves a gene mutation
    • Each step brings cell closer to cancer
    • Clonal expansion of original cell line
    • Normal cell->Altered cell->Initiated cell->Focal lesion->CancerFocal lesion-3 mutations/at risk but not cancer yetCancer-1-2 more mutations/now cancer
  49. Explain tumorigenesis:Colon Cancer
    APC        K-RAS          MMR DEFICIENT  P53   OTHER CHANGES

    Normal epithelium  Early Adenoma Intermediate Adenoma Late Adenoma     Carcinoma Metastasis
  50. Oncogenes
    • 1st identified
    • Over 50 have been identified 
    • Peyton Rous 1911
    • Rous sarcoma virus
    • 1940's he was founded to be right
    •  v-onc-viral derived cancer gene/ reason these viruses were causing cancer
    • positive growth effectors
    • onco-protein is needed for initiation & maintenance of cancer
    • "gas pedal" of cell proliferation
    • not associated with inherited predisposition
  51. Tumor suppression genes
    • negative regulators of cell proliferation
    • only 12-15 identified
    • needed for normal cell growth regulation "brakes" of cell proliferation
    • mutations associated with familial (hereditary) cancer syndromes
  52. Mutator genes
    • DNA repair genes
    • when altered, mutations accumulate more quickly
    • tumorigenesis occurs more rapidly
    • "MUT" genes in excision repair (classes:S,L,H)
    • HNPCC (hereditary nonpolyposis colon cancer)
  53. V-ONC
    • viral derived cancer gene/attach to cell produce cancer
    • reason these viruses were causing cancer
    • high homology
    • occur in cells without viral infection
  54. C-ONC
    • Cellular derived cancer gene
    • altered proto-oncogenes
  55. Proto-oncogenes
    normal cellular genes that promote proliferation
  56. 4 functional groups for oncogenes
    • growth factors
    • growth factors receptors
    • inter-cellular messengers(signal transduction) if mutated can start transductrion on own
    • nuclear effectors(transcription factors)
  57. RAS
    • signal transduction(sarcoma, leukemia)
    • most important oncogene
    • GTP binding (on/off switch )
    • mutations
  58. Proto-oncogene vs. oncogene
    • normal cellular genes that promote cell proliferation
    • cancer gene "gas pedal" to cell profileration
  59. abl
    • signal transduction (sarcomas)
    • abnormal intercellular messengers
  60. src
    signal transduction (lymphoma) abnormal intercellular messengers
  61. erb-b
    growth factor receptor (leukemia)
  62. myc
    nuclear effectors (carcinoma, sarcoma) transcription factor
  63. Tumor suppression genes
    • p53
    • DCC
    • BRCA1- familial breast cancer
    • BRCA2- ovarian cancer
    • APC
    • FAP-familial adenomatous polyposis/ppl have to many polys (can't be removed)very susceptible to colon cancer
    • Rb-2nd important
  64. List the common oncogenes
    • abl
    • src
    • erb-b
    • myc
    • ras
  65. familial cancer vs. sporadic cancer
    • inherited cancer susceptibility
    • born with 1st hit
    • early onset
  66. All about Rb
    • 2nd important tumor suppression gene
    • familial retinoblastoma-bilateral tumors in retinas
    • indirectly binds to G1/S checkpoint (E2F) if it doesnt theres no checkpoint so mutations accumulate quickly 
  67. All about p53/ tp53 (tumor protein 53)
    • 1st important tumor suppression gene
    • Molecular weight: 53kDa
    • Mode of action: transcription factor-maintains G1/S ckpt without it you lose ckpt
    • DNA binding protein/sits at multiple genes
    • Fx: helps protect cells if mutated then Susceptible to cancer
    • Activates regulators of cell proliferations
    • Associated with 50% of sporadic cancers and only 1 familial cancer syndrome
    • Induces apoptosis
  68. Compare & contrast FAP & HNPCC
    familial adenomatous polyposis-individuals have to many polyps to be removed so more suscpetible to colon cancer

    hereditary nonpolyposis colon cancer-15% of colon cancers in US/ no polyps needed/ born with germ line mutation in MUT genes/ susceptible for colon cancer straight from epithelium
  69. CML
    t(9:22) chromosome translocation-chronic myelogenous leukemia formerly known as the Philadelphia chromosome (fusion protein) which is a hybrid gene between chromosome 9 (abl) and chromosome 22 (bcr) both proto-oncogenes which produce a protein that causes cancer
  70. Cell cycle & the effect of oncogenes/tumor suppressor genes
    some genes are gatekeepers, regulators, and caretakers repairing DNA damage to prevent genomic instability
Card Set:
Genetics Final Review
2013-06-28 04:00:18
Genetics Final

Review these for final in genetics
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