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  Chromatin  complex 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 G 1 – normal growth (originally “gap”) S – synthesis of DNA; replication of chromosomes G 2 – 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