Exam 2 Study Guide.docx - Microbiology 160 Exam 2 Study Guide L12 DNA Mutation and Cancer Development Where do mutations come from DNA can acquire

Exam 2 Study Guide.docx - Microbiology 160 Exam 2 Study...

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Microbiology 160 Exam 2 Study Guide L12 DNA Mutation and Cancer Development Where do mutations come from? How do errors in the sequence of DNA (mutations) ultimately matter to function? Translocations How a reciprocal translocation arises Two normal pairs of chromosomes → Parts of two chromosomes break off → and attach to different chromosomes Cancer Tends to Involve Multiple Mutations Benign tumor cells grow only locally and cannot spread by invasion or metastasis Malignant cells invade neighboring tissues, enter blood vessels, and metastasize to different site Timeline: Mutation inactivates suppressor gene → cells proliferate → mutations inactivate DNA repair genes → proto-oncogenes mutate to oncogenes → more mutations, more genetic instability, metastatic disease Cancer Tends to Corrupt Surrounding Environment Growth factors = proliferation Invasive to surrounding areas: blood vessels, matrix, neighboring cells Oncogenes and Cancer Proto-oncogenes code for proteins that help to regulate cell growth and differentiation Proto-oncogenes are often involved in signal transduction and execution of mitogenic signals (stimulating cell division) Oncogenes accelerate cell division and growth Oncogenes are mutated proto-oncogenes or integrated viral genes Oncogenes, when present, accelerate cell growth and division ‘Gain of function’ or pressing the gas pedal You only need 1 oncogenes to give constant ‘gas to the car’ Tumor Suppressor Genes Tumor suppressor genes are a family of normal genes that instruct cells to produce proteins that restrain cell growth and division Since tumor suppressor genes code for proteins that slow down cell growth and division, the loss of such proteins allows a cell to grow and divide in an uncontrolled fashion The Brakes of the Cell Cycle Tumor suppressor genes are like the brake pedal of an automobile The loss of a tumor suppressor gene function is like having a brake pedal that does not function properly, thereby allowing the cell to grow and divide continually Mutations in Tumor Suppressor Genes Normal genes (regulate cell growth) → first mutation (susceptible carrier) → second mutation or loss (leads to cancer) If a tumor suppressor gene produces a stop sign, it must lose both copies of the gene to lose the stop signal
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DNA Repair Genes DNA repair genes code for proteins whose normal function is to correct errors that arise when cells duplicate their Dna prior to cell division Mutations in DNA repair genes can lead to failure in repair which in turn allows subsequent mutations to accumulate People with a condition called xeroderma pigmentosum have an inherited defect in a DNA repair gene
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