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Embryonic Development of Multicellular OrganismsEmbryonic development: zygote à organism1. cell division: large #identical cells through mitosis2. cell differentiation: cells become specialized in structure and function.3. Morphogenesis – creation of form – organism’s shape Determination: irreversible series of events that lead to cell differentiation-Cytoplasmic determinants: maternal substances in egg distributed unevenly in early cells of embryo-Induction: cells triggered to differentiate-cell-cell signals: molecules produced by one cell influences neighboring cells Pattern Formation: setting up the body plan (head, tail, L/R, back, front)-Morphogens – substances that establish an embryo’s axes-Homeotic Genes: master control genes that control pattern formation (eg. Hox genes) Cancer results from genetic changes that affect cell cycle controlControl of Cell Cycle:1. proto-oncogene = stimulates cell division2. tumor-supressor gene = inhibits cell divisionMutations in these genes can lead to cancerex: protein overexpressed – cellcycle over stimulated – increased cell division ex: protein absent, cell cycle not inhibited – increased cell division proto-oncogene à oncogene-proto-oncogene – gene that stimulates normal cell growth and division-oncogene – mutation in proto-oncogene. Cancer-causing gene. Causes increased product of proto-oncogene or increased activity of each protein molecule produced by gene Genes Involved in Cancer:-Ras gene: stimulates cell cycle (proto-oncogene)--mutations of ras occurs in 30% of cancers-p53 gene: tumor-supressor gene--functions: halt cell cycle for DNA repair, turn on DNA repair, activate apoptosis (cell death)--mutations of p53 in 50+% of cancers-cancer results when mutations accumulate (5-7 changes in DNA)-active oncogenes + loss of tumor-supressor genes-the longer we live, the more likely cancer might develop Summary: -embryonic development occurs when gene regulation proceeds correctly-cancer occurs when gene regulation goes awry
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