Ch 12 RQ

1. What functions is MITOSIS used for in the body?

2. What is ALL of the DNA in a cell known as?

3. Nuclear division is also called ____.4. The division of the cytoplasm is called

______.5. 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.

1. The complete genome is duplicated during interphase- these become sister chromatids (2 identical copies)

2. Cell division occurs after duplication in two phases nuclear and cytoplasm

(mitosis) (cytokinesis)

3. Describe how chromosome number changes throughout the human life cycle.

1. Individual inherits 46, 23 from each parent

2. Meiosis halves number to 23 (sperm or ovum)

3. Fertilization (23 + 23 = 46)

4. Zygote has 46 new chromosomes

5. 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 = growth2. S phase = synthesis (duplication)3. G2 phase = growth

B. Mitosis & Cytokinesis nuclear & cytoplasmic division1. Prophase2. Prometaphase3. Metaphase4. Anaphase5. Telophase6. 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 outPrometaphase 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.

Animals- process called

‘cleavage’1. Cleavage furrow

forms a shallow groove in the cell surface

2. Contractile ring of actin forms and contracts

3. 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

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