Raven & Johnson Chapter 10 Campbell Chapter 12 THE CELL CYCLE

SOME DEFINITIONS  Genome – full set of genetic info  Chromosomes – way DNA is packaged  Gametes – reproductive cells  23 chromosomes  Somatic cells – all but reproductive cells  46 chromosomes

SOME DEFINTIONS Chromatin – DNA-protein complex – uncoiled DNA fiber One double-chromosome has two sister chromatids Chromatids joined at centromere

SOME DEFINTIONS Produce gametes in gonads through meiosis Produce somatic cells through mitosis & cytokinesis

CELL CYCLE - OVERVIEW  M phase (mitosis) – 10% of cycle  Interphase (non-dividing) – 90%  Divided into G 1, S, G 2 phases  Cell grows (makes proteins & organelles)  Copies chromosomes in S (synthesis) phase  G 1  S  G 2  M  M – 5 phases M – 5 phases

THE MITOTIC SPINDLE Begins assembly in centrosome (organizes microtubules) Interphase – centrosomes replicate Prophase & prometaphase – move to opposite ends of cell & microtubules grow from them – now spindle poles

THE MITOTIC SPINDLE Spindle fibers attach to chromosome’s kinetochore Complete when chromosomes line up along metaphase plate

THE MITOTIC SPINDLE Anaphase – proteins joining chromatids inactivate  kinetochore motor proteins “walk” chromatid to pole  microtubules shorten

CYTOKINESIS  Animal cells go through cleavage  Starts with cleavage furrow (shallow groove)  Actin & myosin involved  Plant cells make cell plate  Vesicles from Golgi bodies come together and bring together cell wall material

EVOLUTION OF MITOSIS Prokaryotes  binary fission Single bacterial chromosome – circular DNA & proteins As DNA replicates, copies of first replicated region (origin of replication) move apart Cell grows & splits plasma membrane

Replication of E. coli

CELL CYCLE REGULATION (INTERNAL) Critical control points where stop & go signals regulate cycle Signal-transduction pathways at G 1, G 2, and M If, at G 1, it cannot continue (or does not need to), it exits cycle & moves into G 0 (nondividing) phase Most cells in G 0 phase until need to divide

CELL CYCLE REGULATION  Kinases drive cell cycle when activated – activated when attached to cyclin (protein that fluctuates conc. in cell)  called cyclin- dependent kinases (Cdk)  Cdk activity rises when cyclin conc. rises  Cyclin-Cdk complex is called MPF  Maturation Promoting Factor (M-phase PF)  Triggers cell from G 2 into M

CELL CYCLE REGULATION

Cdk now stays inactive until joining with new cyclin during next turn of the cycle Checkpoints

CELL CYCLE REGULATION M-phase checkpoint makes sure chromosomes are attached at metaphase plate before anaphase Kinetochores not yet attached send out a delay signal Keeps anaphase-promoting complex (APC) inactive until all are attached

CELL CYCLE REGULATION Cell Cycle Checkpoints Video on mitosis and meiosis (we will view just checkpoints here)Video on mitosis and meiosis (we will view just checkpoints here)

CELL CYCLE INFLUENCES (EXTERNAL)  Growth factors – protein released by body cells to stimulate cell division  Ex: Platelet-derived growth factor (PDGF)  Density-dependent inhibition  Crowded cells stop dividing  Anchorage dependence  Must be attached to substrate (tissue, petri dish) to divide

CANCER No density-dependent inhibition Doesn’t stop when growth factors deplete Divide & stop randomly – don’t adhere to checkpoints Divide indefinitely if nutrients present Transformation: normal cell  cancer cell

CANCER Tumor: mass of abnormal cells Benign – remains at original site Malignant – invasive; impairs functions of one or more organs Metastasis – spread of cancer cells to other distant parts of the body

9:18 WHO OWNS YOUR CELLS?????