1. Cell division functions- _________________________ and ____________ Cell division requires the distribution of identical genetic material - DNA - to two daughter cells. A dividing cell _____________ its DNA, allocates the two copies to opposite ends of the cell, and then splits into two daughter cells. Fig. 12.2c CHAPTER 12 THE CELL CYCLE

2. Cell division distributes identical sets of chromosomes to daughter cells A cell’s genetic information, packaged as DNA, is called its _________. In prokaryotes, the genome is often a _________ DNA molecule. In eukaryotes, the genome consists of ________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. Fig. 2.3

_________ - The process of the formation of the two daughter nuclei from a single parental cell is usually followed by division of the cytoplasm, _____________. Result- two cells that are the genetic equivalent 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 Fig 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

Chromosome duplicated Chromosomes coiled Sister chromatids joined Mitotic spindle forms Nucleoli disappear Nuclear envelope fragments Microtubles attach to kinetochores on centromere Fig left 1. _________ 2. _________3. _____________ Mitosis- 6 phases

Sister chromatids arranged in “Plate” by spindles 4. __________5. _______6. ____________________ Centromeres divide Chromosomes pulled to poles Nuclei begin forming Chromatin relaxes Cytokinesis begins Mitosis Fig right

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 Assembly of the spindle microtubules starts in the ______________. As the spindle fibers grow from them, the centrioles are pushed apart. By the end of prometaphase they develop as the ___________ at opposite ends of the cell. _______________ (at centromere) are attachment points to spindle Fig. 12.7

5. 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 ______. Fig. 12.9a Fig. 12.9b

6. Prokaryotes reproduce by ___________, not mitosis. Bacterial genes located on a single chromosome which consists of a circular DNA molecule and associated proteins. 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. Fig

The cell cycle is driven by specific __________ signals. Evidence-Fusion of an M phase and a G 1 phase cell, induces the ___nucleus to start __ phase. 7. A molecular control system drives the cell cycle Fig 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 Three major checkpoints are found in the __, ___, and __ phases. A ___________ in the cell cycle is a critical control point where stop and go signals regulate the cycle. If it does not receive a go-ahead signal, the cell exits the cycle and switches to a nondividing state, the __ phase. Most human cells are in the G0 phase

Answer- ______________ regulate cell cycle by activate or deactivate other proteins by _________________. What controls cell cycle? But these kinase levels remain constant throughout cell cycle. Answer- ______. So what activates the kinases? Level of cyclin proteins fluctuate cyclically. The complex of kinases and cyclin forms _____- ________________________ ______ levels rise sharply throughout __________, then fall abruptly during _________. Kinase MPF is a __________ complex Fig a

____ (“maturation-promoting factor”) triggers the cell’s passage past the ___ checkpoint to the __ phase. MPF… _______________ by phosphorylating a variety of other protein kinases. ___________ ______________ of the nuclear envelope. ______________ _______________ Fig b Other cyclins and cdks are involved at other cell cycle checkpoints

8. 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 _____. Fig

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. Fig 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. 9. 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 ___________, 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 A typical cancer senario- breast cancer Treatments for metastasizing cancers include __________ ____________ and _______________ with toxic drugs. These treatments target actively ____________ cells.