Download - Cell Division Stimulants DNA overload Exchange of material- ratio of surface area to volume
Cell Division
Stimulants• DNA overload• Exchange of material- ratio of
surface area to volume
Cell Cycle Regulators• Cyclins: proteins that regulate the
timing of the cell cycle in eukaryotic cells
Internal Regulators• Respond to events inside the cell
-ex: stops cell from entering mitosis until all chromosomes are replicated-ex: prevents anaphase until all chromosomes are attached to spindles
External Regulators• Respond to events outside the cell• Direct cells to speed up or slow down cycle
ex: growth factors- most importantduring embryonic development and
wound healingex: neighboring cells’ surface molecules slow down cycles (prevents excessive growth & disruption to other tissues)
Proto-oncogenes
• Code for regulatory proteins• Mutation: Oncogene (causes uncontrolled
cell proliferation)
Tumor-suppressor Genes
• Code for proteins that prevent cell division• Mutations – cause cancer
Cancer
• Uncontrolled cell division• Form tumors – mass of cells–Benign- remain in mass (Can compress
vital organs)–Malignant- invade tissues
• Results from mutations• Chromosomes in cancer cells are unstable–
rearrangements, duplications, deletions
Cancer• Cells lose ability to control growth• Causes: smoking, radiation, viruses,
chemicals• Can metastasize- break off & travel
through body- Don’t recognize that they are not attached
• Defect in gene p53 (halts cell cycle until all chromosomes properly replicated)