AP Biology Chapter 12: The Cell Cycle

cell division
the reproduction of cells, continues life

cell cycle
the life of a cell from the time it is first formed from a dividing parent cell until its own division into two cells

a cells endowment of DNA, its genetic material

DNA molecules are packed into these, makes the replication and distribution of DNA manageable

somatic cells
any body cells except the reproductive cells. each contain 46 chromosomes made up of two sets of 23, one from each parent

reproductive cells, sperm and egg. have half as many chromosomes as somatic cells. they have one set of 23.

what eukaryotic chromosomes are made of. complex DNA and associated protein molecules.

sister chromatids
each duplicated chromosome has two of these. the two chromatids, each containing an identical DNA molecule, are initially attached by adhesive proteins along their lengths

the narrow “waist” region where the two chromatids are most closely attached

the division of the nucleus

the division of the cytoplasm

the production cycle of gametes, yields nonidentical daughter cells that have only one set of chromosomes, thus half as many chromosomes as the parent cell. occurs in gonads

mitotic (M) phase
mitosis and cytokinesis, the shortest part of the cell cycle

alternates with the mitotic phase, accounts for 90 percent of the cell cycle. the cell grows and copies its chromosomes in preparation for cell division. divided into 3 phases: G1, S, G2

G1 phase
first gap of interphase, cell grows by producing proteins and cytoplasmic organelles such as the mitocondria and er, copies chromosomes

S (synthesis) phase
chromosomes are duplicated during this plase, continues growth

G2 phase
second gap. grows more as it completes preparation for cell division

mitotic spindle
begins to form in the cytoplasm during prophase. this structure consists of fibers made of microtubules and associated proteins

where assembly of spindle microtubules starts, a nonmembraneous organelle that functions throughout the cell to organize the cell’s microtubules

a radical array of short microtubules, extends from each centrosome. the spindle includes the centrosomes, the spindle microtubules, and this

a structure of protiens associated with specific sections of chromosomal DNA at the centromere. each of the two sister chromatids has this

G2 of Interphase
-a nuclear envelope bounds the nucleus

G2 of Interphase
-the nucleus contains one or more nucleoli

G2 of Interphase
-in animal cells, each centrosome features two centrioles

G2 of Interphase
-chromosomes, duplicated during S phase, cannot be see individually because they have not yet condensed

-the chromatin fibers become more tightly coiled, condensing into discrete chromosomes observable with a light microscope

-the nucleoli dissapear

-each duplicated chromosome appears as two identical sister chromatids joined together

-the mitiotic spindle begins to form. it is composed of the centrosomes and the microtubules that extend from them. the radial arrays of shorter microtubules that extend from the centrosomes are asters

-the centrosomes move away from each other, apparently propelled by the lengthening microtubules between them

-the nuclear envelope fragments

-the microtubules of the spindle can now invade the nuclear area and interact with the chromosomes, which have become even more condensed

-microtubules extend from each chromosome toward the middle of the cell

-each of the two chromatids of a chromosome now has a kinetochore, a specialized protein structure located at the centromere

-some of the microtubules attach to the kinetochores, becoming “kinetochore microtubules” these jerk the chromosomes back and forth

-nonkinetochore microtubules interact with those from the opposite pole of the spindle

-the longest stage of mitoisis lasting 20 minutes

-the centrosomes are now at opposite ends of the cell

-the chromosomes convene on the metaphase plate, an imaginary plane that is equidistant between the spindles two poles. the chromosomes cetromeres lie on the metaphase plate.

-for each chromosome, the kinetochores of the sister chromatids are attached to kinetochore microtubules coming from opposite poles

-the entire apparatus of microtubules is called the spindle because of its shape

the shortest stage of mitosis, lasting only a few minutes

begins when the two sister chromatids of each pair suddenly part. each chromatid this becomes a full fledged chromosome

-the two liberated chromosomes begin moving toward opposite ends of the cell, as their kinetochore microtubules shorten. because these microtubules are attached at the centromere region, the chromosomes move centromere first.

-the cell elongates as the nonkinetochore microtubules tighten

-by the end of this stage, the two ends of the cell have equivilent and complete collections of chromosomes

-two daughter nuclei begin to form in the cell

-nuclear evelopes arise from the fragments of the parent cell’s nuclear evelope and other portions of the endomembrane system

-the chromosomes are less condensed

-mitosis, the division of one nucleus into two genetically identical nuclei, is now complete

-the division of the cytoplasm is usually well underway by late telophase, so that the two daughter cells appear shortly after the end of mitosis

-in animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two

origin of replication
the specific place the chromosome begins to replicate

cell cycle control system
cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle.

in the cell cycle, a critical control point where a stop and go ahead signal is given regulates the cycle. usuallyif it passes G1 it goes all the way, baby

G0 phase
if it does not recieve a go ahead signal at that point, it will exit the cycle, switching into a nondividing state. most cells in the human body are in this phase.

in order for the kinase that drives the cell cycle to actually be active in the cell, it must be attached to one of these. this cyclically fluctuates at a concentration in the cell

cyclin dependent kinases
cdks. activity of these rise and falls with the level of the cyclin partner

growth factor
a protein released by certain cells that stimulates other cells to divide. mitogen

density-dependent inhibition
when crowded cells stop dividing. the amount of growth factors provided are the main factor to determine this

anchorage dependence
exhibited by most animal cells. to divide, cells must be attached to a substratum such as the inside ofa culutre jar, or the extracellular matrix

the spread of cancer cells to locations distant from their original site

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