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Ch. 12: The Cell Cycle
KEY CONCEPTS Cell division results in genetically
identical daughter cells The mitotic phase alternates with
interphase in the cell cycle The eukaryotic cell cycle is regulated
by a molecular control system
Key Roles of Cell Division Reproduce more of your own kind
R.Virchow in 1855 “Omnis cellula e cellula” (Every cell comes from a cell)
Amoeba or plant cuttings Physically pass a copy of the ‘information’ on
to the next generation Produce eggs and sperm, pollen, spores
Meiosis is a form of cell division Growth
Larger organisms (toddler to teen) Renewal
Replace shed skin cells Repair
Fix a wound
Genetically Identical Daughter Cells
Copying of genetic material Accuracy generation after generation
Equal distribution of genetic material copies Precision – with no dilution
Even distribution of cytoplasm and membrane
Physical separation of the two new cells Each cell is half of the parent, parent
doesn’t exist as an individual anymore, yet isn’t gone……
Chromosome Redistribution
Genome entire genetic information for an individual or species
Chromosomes manageable packages of DNA
Somatic cells body cells, contain a set number of chromosomes for their species; humans 23 pairs (46)
Gametes reproductive cells like egg and sperm that have only 1 of each chromosome; humans one set of 23
Chromatincomplex of protein and DNA that is very long and linear
More terminology
Sister chromatids duplicated chromosomes, identical information, initially attached to each other
Centromere waist region of chromatid (arm and cohesions)
Mitosis division of a eukaryotic nucleus
Cytokinesis division of the cytoplasm
Meiosis process that generates gametes
The Cell Cycle
Interphase G1 – normal growth (originally “gap”) S – synthesis of DNA; replication of chromosomes G2 – extra proteins and cytoplasmic organelles
like mitochondria Mitotic Phase - “mitosis”
Prophase Prometaphase Metaphase division of the nucleus Anaphase Telophase
Cytokinesis - physical division of the cytoplasm
Phases of mitosis
Details of Phases
Interphase G1- gap one, not much visible, cell is
growing, normal- everyday life, accessing DNA, making proteins
S – synthesis of new DNA, all or nothing event, replication of chromosomes in entirety
G2 – now ready to divide nucleus, produce new structures for after division like ER and mitochondria
Details of phases
Mitosis Prophase – chromatin is chromosomes, visible
structure, packaged format Prometaphase – centrosomes move apart,
spindle forms, spindles attach to kinetochores, tug-o-war
Metaphase- phase where chromosmes are aligned at equator
Anaphase – chromosomes are in motion, sister chromatids are separate
Telophase – 2 separate nuclei, return to chromatin
Details of phases
Cytokinesis Still part of mitosis (Interphase +
Mitosis = Cell Cycle) This is division of cytoplasm, as
opposed to division of the nucleus Overlaps with both interphase and
telophase (see pg 231)
Plant vs Animal
Binary fission
Mitosis, binary fission and in between
Binary fission = prokaryotes One chromosome No nuclear
membrane Less to organize
Mitosis = eukaryotes Multiple
chromosomes Nuclear membrane Organelles to
organize
Regulation of the cell cycle
Cytoplasmic (chemical) regulation Mechanical (physical) regulation
Separate PPT
Lack of regulation in the cell cycle Cells which don’t respond to check point
signals within the cell or to physical conditions like contact tend to divide out of control and are called cancer cells. Own blood supply Use lots of nutrients Transformation turns normal cell into cancer
cell (related to microtubles, genetic? environmental? )
Mass of extra cells is tumor (benign) Malignant tumors invade other tissues and
organs Spreading of cancer cells is called metastasis