1. Cell division functions-___________,_____________ and ___________________• Cell division requires the distribution of

_________ genetic material (DNA) to two __________ cells.

Fig. 12.1c

CHAPTER 8Cell Division and Mitosis

2. Cell division distributes identical sets of chromosomes to daughter cells

• A cell’s genetic information, packaged as DNA, is called its _____________

• In prokaryotes, _______ DNA molecule.

• In eukaryotes,- _____ DNA molecules.

• DNA molecules are packaged into _____________

• Every eukaryotic species has a characteristic number of chromosomes in the nucleus.

• Human __________ (body cells) have 46 chromosomes.

• Human _______sperm or eggs) have 23 chromosomes, half the number in a somatic cell.

______ - The process of the formation of the ____ daughter nuclei from a single parental cell

• is usually followed by division of the cytoplasm, _________________.

• Result- two cells that are the genetic __________ of the parent.

_______ – one parental cell produces __ daughter cells

• Occurs only in the ______(ovaries and testes),

• Result- Each cell has half the chromosomes.

• In humans, meiosis reduces the number of chromosomes from __to ___

• Fertilization fuses two ______ together and doubles the number of chromosomes to ___ again.

• The ___________ of the cell cycle alternates with the much longer ________.

• The M phase includes ____ and __________.

• Interphase accounts for ____ of the cell cycle.

3. The mitotic phase alternates with interphase in the cell cycle: an overview

Interphase has three subphases:•the _______ (“first gap”) centered on growth•the _____ (“synthesis”) when the chromosomes are copied •the ______ (“second gap”) where the cell completes preparations for cell division

G1

G2

S

M

•Chromosome _________ •Chromosomes coiled•Sister ________joined•Mitotic _______ forms•_________ disappear

•Nuclear envelope _________•Microtubles attach to _________ on centromere

Fig. 12.5 left

1. __________ 2. _________3. _____________

Mitosis- 6 phases

•Sister chromatids arranged in “_____” by spindles

4. __________ 5. ________ 6. ________and ____________

•Centromeres divide•Chromosomes pulled to poles

•Nuclei begin forming•Chromatin relaxes•____________ begins

Mitosis

• The ________________

• fibers composed of _________and associated proteins

• is a major driving force in __________.

• Assembled during _______from cytoskeleton components.

• The spindle fibers elongate by incorporating more subunits of the protein tubulin.

4. The ____________ distributes chromosomes to daughter cells

Cytokinesis divides the cytoplasm• ____________

• follows ______

• In animals- A contractile ring of ____ microfilaments and the motor protein ______ form to pinch the cell in two.

• In plants- vesicles from the Golgi coalesce at the metaphase plate, forming a _________.

• The plate enlarges until its

membranes ______

vesicles converging

5. Prokaryotes reproduce by __________, not mitosis.

• Bacterial genes located on a single chromosome

• In binary fission, chromosome replication begins at one point in the circular chromosome, the __________________ site.

• These copied regions begin to move to opposite ends of the cell.

• Mechanism is unknown• ______________ are unknown in bacteria.

• The cell cycle is driven by specific _________signals.

• Evidence-Fusion of an M phase and a G1 phase cell, induces the __ nucleus to start ___ phase.

6. A molecular control system drives the cell cycle

Fig. 12.12

• The _______ and _____ of cell division varies with cell type.• Skin cells divide often, mature nerve and muscle cells not at all

• The distinct events of the cell cycle are directed by a distinct cell cycle ___________________.

Fig. 12.13

Three major checkpoints are found in the __-___ , and __ phases.

A ___________ - control point where stop and go signals regulate the cycle.

If no go-ahead signal, the cell exits the cycle and switches to a nondividing state, the ___ phase.

•Most human cells are in the G0 phase

7. Internal and external cues help ________ the cell cycle

• Growth factors stimulate cells to ________

Example: Platelet-derived growth factors (PDGF), produced by platelet blood cells, bind to tyrosine-kinase receptors of fibroblasts, and triggers a signal-transduction pathway that leads to cell division.

• The role of _____ is easily seen in cell culture.

• Fibroblasts in culture will only divide in the presence of medium that also contains PDGF.

Fig. 12.15

• Growth factors appear to be a key in_______-_______________________ of cell division.

• Cultured cells normally divide until they form a ___________ on the inner surface of the culture container.

• If a gap is created, the cells will grow to fill the gap.

Most animal cells also exhibit _______ __________for cell division.

•Must be anchored to a __________, typically the ____________________ of a tissue

• Cancer cells divide excessively and invade other tissues because they are free of the body’s control mechanisms.

• If and when cancer cells stop dividing, they do so at random points, not at the ______________ in the cell cycle.

8. Cancer cells have escaped from cell cycle controls

•Cancer cells are free of both 1-____________________ and 2-_________________________.

• Cancer cell may divide indefinitely if they have a continual supply of ________________.

• In contrast, nearly all mammalian cells divide _______ times under culture conditions before they stop, age, and die.

• ________________- a single cell in a tissue converts to a cancer cell.

• Normally, the immune system recognizes and destroys transformed cells.

• However, cells that evade destruction proliferate to form a tumor, a mass of abnormal cells.

• ________ tumor- The abnormal cells remain at the originating site.

• __________ tumor- the abnormal cells leave the original site to impair the functions of one or more organs (Known as __________).

• _________- Cancer cells are carried by the blood and lymph system to new sites and start more tumors.

Fig. 12.17

A typical cancer senario- breast cancer

• Treatments for metastasizing cancers include high-energy ______________ and _____________with toxic drugs.

• These treatments target actively __________cells.