BSC1010C Lecture Notes - Lecture 21: Central Nervous System, Brca1, Metaphase
Document Summary
All dna contained in the cell: chromosome. A unit of dna polymer in a cell. Dna is wrapped around proteins called histones: chromosomes visible under a microscope are condensed, condensed chromosomes only occur prior to cell division, gene. Do all our cells always divide: cells we constantly replace: Intestinal surfaces: cells that adults do(cid:374)"t (cid:374)or(cid:373)ally replace: Heart muscle cells: wound healing triggers cell division! Growth 1 (g1) --- protein, lipid, carbo synthesis, energy generation. Growth 2 (g2) --- protein, lipid, carbo synthesis, energy generation. Multiple checkpoints before the mitosis stage occurs. G1 checkpoint: dna must be undamaged, cell size must be adequate, sufficient amount of nutrients, social signals present, mature cells do not pass this checkpoint and enter the g0 state. G2 checkpoint: chromosomes replicated successfully, dna is undamaged, activated mitosis promoting factor (mpf) is present. Metaphase checkpoint: all chromosomes attached to spindle apparatus, cyclin proteins regulate the cell cycle. They cycle levels as the cell grows.
