handout 4.5.11 - 1 Neutral theory of molecular evolution...

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1 4/5/11 1. Neutral theory of molecular evolution Argues that most allelic variation in a gene pool or between species is due to the genetic drift of neutral and slightly deleterious alleles rather than to natural selection 2. Bottleneck Refers to a temporary past reduction in the size of a population during which drift occurred and genetic variation was thereby lost 3. Founder effect Random allele frequency change in a new small (founder) population due to sampling errors as it splits from its larger parental population ------------------------------------------------------------------------------------------------------------------------------------------- CANCER FIVE CLASSIC EXAMPLES A. Burkitt’s lymphoma Reciprocal translocation between autosomes 8 and 14 moves the myc proto-oncogene from a weak promoter into close proximity of strong enhancers for immunoglobin (antibody) expression in white blood cells (wbc) End result is over-expression of myc protein, and thereby, overstimulation of white blood cell proliferation B. Leukemia due to retroviral integration into human host DNA Gene therapy for X-linked form of severe combined immunodeficiency (X-SCID) using a recombinant retrovirus In two children, this recombinant retrovirus inserts in or next to LMO2 gene, thereby activating it This activation results in over-proliferation of white blood cells (wbc) A. Missense mutation in ras proto-oncogene Single amino acid change prevents the hydrolysis of bound GTP into GDP by ras Thus, ras becomes fixed in its active, GTP-bound state This continuously active ras sends a constant message for cell division to the cell nucleus via the internal signal transduction pathway B.
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