Ch 12 RQ

2. 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?

4. 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 

5. 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) 

7. 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 

8. 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 

10. 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) 

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

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

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

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

21. 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) 

22. 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 

23. 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) 

25. Animals 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  9. Compare cytokinesis in animals and plants.

27. 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 

28. 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 

30. 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)  12. Describe the internal and external factors which influence the cell cycle control system.

33. 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 