Ch 12 RQ What functions is MITOSIS used for in the body? What is ALL of the DNA in a cell known as? Nuclear division is also called ____. The division of the cytoplasm is called ______. What is the process by which gametes are produced?

1. Describe the structural organization of the genome. Genome = the total hereditary endowment of a cell Organized into functional units called chromosomes (supercoiled DNA-protein complexes of chromatin) The DNA exists in different phases at different stages in the cell cycle 

2. Overview the major events of cell division that enable the genome of one cell to be passed on to two daughter cells. The complete genome is duplicated during interphase - these become sister chromatids (2 identical copies) Cell division occurs after duplication in two phases  nuclear and cytoplasm (mitosis) (cytokinesis) 

3. Describe how chromosome number changes throughout the human life cycle. Individual inherits 46, 23 from each parent Meiosis halves number to 23 (sperm or ovum) Fertilization (23 + 23 = 46) Zygote has 46 new chromosomes Becomes an individual 

4. List the phases of the cell cycle and describe the sequence of events that occurs during each phase. A. Interphase  growth & metabolic activity - 90% of cell cycle 1. G1 phase = growth 2. S phase = synthesis (duplication) 3. G2 phase = growth Mitosis & Cytokinesis  nuclear & cytoplasmic division 1. Prophase 2. Prometaphase 3. Metaphase 4. Anaphase 5. Telophase 6. Cytokinesis 

5. List and draw the phases of mitosis and describe the events characteristic of each phase. Prophase Nucleoli disappear Chromatin condenses into chromosomes Spindle and centrosomes form (act as anchors) 

Prometaphase… Nuclear envelope fragments Spindle fibers extend Kinetochore at the centromere region Kinetochore microtubules attach Nonkinetochore radiate and overlap with others 

Metaphase… Centrioles position at opposite poles Chromosomes move to the cell’s equator and centromeres align 

Anaphase… Characterized by movement Sister chromatids split apart Kinetochore microtubules shorten Poles move further apart, elongating the cell 

Telophase & cytokinesis… Nonkinetochore microtubules elongate cell Daughter nuclei begin to form Nuclear envelopes form Nucleoli reappear Chromosomes uncoil Cytoplasm divides 

6. Draw or describe the spindle apparatus including centrosomes, nonkinetochore microtubules, kinteochore microtubules, asters, and centrioles (in animal cells). The assembly of spindle microtubules begins in the centrosome, or microtubule organizing center Nonkinetochores elongate the whole cell during anaphase Kinetochores arrange chromosomes and align them Centrioles  the center of the centrosome (not necessary and only found in animal cells) 

7. Describe what characteristic changes occur in the spindle apparatus during each phase of mitosis. Prophase spindle microtubules radiate out Prometaphase  each chromatid develops kinetochores -spindles attach and become kinetochore microtubules Metaphase  all duplicated chromosomes align at plate (equator) Anaphase  centromeres split – microtubules direct segregation; kinetochore microtubules shorten by depolymerizing ends Telophase  sets of chromosomes are clustered at ends 

8. Explain the current models for poleward chromosomal movement and elongation of the cell’s polar axis. Kinetochore microtubules shorten at the kinetochore end as chromosomes approach poles Microtubules shorten by depolymerizing at the ends; pulling chromosomes apart The mechanism of this interaction may involve microtubule-walking proteins that “walk” a chromosome (between kinetochores and microtubules) 

9. Compare cytokinesis in animals and plants. process called ‘cleavage’ Cleavage furrow forms a shallow groove in the cell surface Contractile ring of actin forms and contracts Parent cell pinches into two Plants - cell plate grows and eventually divides cell into two joined cells 

10. Describe the process of binary fission in bacteria and how this process may have evolved to mitosis in eukaryotes. A process during which bacteria replicate their chromosomes and equally distribute the copies Preceded eukaryotic cell division - origins of mitosis 

11. Describe the roles of checkpoints, cyclin, Cdk, and MPF, in the cell-cycle control system. Checkpoints  ensure that appropriate conditions have been met before the cycle advances Cyclin  a class of regulatory proteins that control cyclical changes in kinase activity CDKs  cyclin-dependent-kinases that regulate the cell cycle when attached to a particular cyclin MPF  maturation promoting factor – controls the cell’s progress through the G2 checkpoint to mitosis 

All chromosomes must be attached External Chemical factors 12. Describe the internal and external factors which influence the cell cycle control system. Internal Kinetochores signal the M- phase checkpoint about chromosome – spindle interactions All chromosomes must be attached External Chemical factors - lack of essential nutrients - growth factors needed Physical factors - crowding (density-dependent inhibition) - need substrate (anchorage-dependent inhibition) 

13. Explain how abnormal cell division of cancerous cells differs from normal cell division. Cancer cells have escaped cell cycle controls - divide excessively - do not respond to cell density or lack of growth factors - can make growth factors themselves Products of mutated or transformed normal cells Spread of cancer is called metastasis 