3

Cards (25)

  • Mutation is an abnormal gene change.
    There are 2 types – acquired and inherited
    Inheritedpresent in every cell in body. Passed down from parent to child
    Acquired – get mutations at some point of your life. More common than inherited. Present only in one cell and is passed down to offspring of that cell.
    Mutations can produce polymorphism
  • Mutagenesismutagens are all chemical carcinogens.
    Ames test – helps to see if a substance can be carcinogenic.
    Bacterial cultures are present to see any mutations. Liver extract with chemical is added to these cultures. Added after metabolic activation has occurred.
    Positive result – substance can be carcinogenic
  • DNA damagerepaired by DNA repair enzymes.
    Rate error of mitotic cell increases carcinogens. Interfere with normal repairing.
  •  DNA lesionsdamaged sites on DNA structure
    Abasic site – DNA base missing. Due to pH drop, temperature rise and base alkylations.
    Mismatchreplication errors. Due to tautomerization and spontaneous deamination.
    Modified bases – lesions due to base changes. UV induced.
  • Mismatch lesion
    A) mismatch
  • Abasic lesion
    A) abasic site
  • modified bases
    A) modified bases
  • Single strand breaksgap in one strand of backbone. Due to oxygen radicals, ionizing radiation and peroxides.
    Interstrand crosslinkscovalent linkage between 2 strands. No DNA replication past lesion. Helicase cant break linkage.
    Double stranded breakslethal. Gaps in both strands of backbone. Due to ionizing radiation
  • Single stranded breakage
    A) single stranded break
  • interstrand crosslinks
    A) interstrand crosslinks
  • double stranded breals
    A) double stranded breaks
  • Viral DNA damageoncovirus can infect and cause tumor.
    Viral replication - interrupt host replication. Cell cycle is affected.
    Oncoviruses may use host for increased replication.
  • Reverse trancribed DNA inserted into host cell. Host cell begins to replicate oncogenes as well as viral proteins.
  • Chromosome damagecell cycle genes moved to another chromosome due to chromosomal translocation.
  • DNA repair mechanism – nuclease cuts out damaged DNA
    DNA polymerase adds correct nucleotide
    DNA ligase closes gaps on backbone
  • 3 major DNA repair mechanisms - mismatch, base excision and nucleotide excision repair.
  • Mismatch repair – after DNA replication new strand not methylated.
    Mismatched base pair cleaved by mut proteins
    Cleavage by exonuclease
    Gap filled by polymerase I
    Ligase closes gaps on backbone
  • Nucleotide excision repair – cleavage by endonuclease. Damaged nucleotides removed by proteins. Gap filled by polymerase I. gap on backbone closed by ligase.
  • Base excision repairDNA glycosylase forms abasic site (AP). AP endonuclease removes AP site. DNA polymerase I fills gaps. DNA ligase closes gaps on backbone.
  • Other DNA repair mechanisms – no parental strandhomologous chromosome can replace damaged chromosome
    No parental strand or homologous chromosomenon homologous chromosome can replace damaged chormosome
  • Without DNA damagexeroderma pigmentosumnucleotide excision repair enzyme defect. Leads to skin cancer. DNA damage can’t be repaired due to UV light.
  • Gene mutations lead to cancer. 2 genes involved in cancer.
    Oncogenes – genes that turn normal cells to cancer cell.
    Tumour suppressor genes – normal genes that control cell division repair DNA damage.
    Tumour suppressor inactivation - cancer
    Oncogene activation - cancer
  • ProtoncogenesC-myc and Ras
    Tumor suppressor genes – BRAC 1 and 2, P53 and P16
  • synergistic mutagens – in the same cell if p53 and Ras are mutated, they can control a group of genes that can lead cells to become cancerous and make tumors grow.
  • Inheritance and cancer genetics – there is an increased risk of cancer when a faulty gene is passed down from parents to child.
    Cases of rare cancer, cancers at young ages, multiple cancers in one person…
    Hereditary cancers are colorectal and papillary renal cancer