SC- B-2.6: Summarize the characteristics of the cell cycle: interphase;the phases of mitosis, and plant & animal cytokinesis
2 main reasons cells divide instead of growing larger 1. DNA overload larger cells have greater demand on DNA 2. trouble moving nutrients & wastes in/out of cell surface area/vol ratio: larger ratios more efficient
in nuclei of eukaryotic cells made up of: 1. DNA 2. Histones: proteins DNA wraps around
series of events that cells go through as they grow & divide only in eukaryotic cells What a cell does in the cell cycle: grow prepares for division divides into 2 daughter cells
The Cell Cycle
time between cell divisions 3 divisions: 1. Gap 1 (G1) 2. S Phase 3. Gap 2 (G2)
cells do most of their growing make proteins & organelles checkpoint cells destined never to divide again leave cell cycle & enter G0
synthesis phase chromosomes duplicated cells that enter S destined to go thru mitosis
usually shortest part of interphase material needed for cell division produced checkpoint
4 phases: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase each phase may last minutes to days depending on cell type completion: 2 nuclei
longest phase of mitosis chromosomes become visible (chromatin condenses) centrioles separate & move to opposite sides of nucleus (animal cells )
centrioles start to organize mitotic spindle nuclear envelope & nucleolus disappears
chromosomes line up across center of cell = metaphase plate centromere of each chromosome connected to spindle fiber
centromeres split pulling sister chromatids apart as soon as split they are called chromosomes as long as they are moving they are in anaphase
chromosomes disperse & are no longer visible 2 nuclear envelopes reform & each nuclei starts to form a nucleolus spindle breaks apart cleavage furrow becomes visible
cytoplasm pinches in half each daughter cell has identical set of duplicate chromosomes
rigid cell wall cannot “pinch” in half Cell Plate starts to form during telophase cell wall between 2 daughter cells