Ch. 12 - The Cell Cycle

3 roles of cell division

3 roles of cell division

reproduction, growth and development, tissue renewal

cell cycle

the life of a cell from the time it is first formed during division of a parent cell until its own division into 2 daughter cells

genome

a cell's DNA/genetic information

chromosomes

threadlike structures made of DNA molecules that contain the genes

chromatin

the entire complex of DNA and proteins that is the building material of chromosomes

chromatid

one of two identical "sister" parts of a duplicated chromosome

centromere

area where the chromatids of a chromosome are attached (binded area)

somatic cells

any cells in the body other than reproductive cells

gamete

reproductive cell; sperm & egg

how many chromosomes in a human somatic cell?

46 chromosomes (2 sets of 23)

how many chromosomes in a human gamete?

23 chromosomes (1 set of 23)

mitosis

division of genetic material in the nucleus

meiosis

a type of cell division that results in sperm/egg production

Mitosis or meiosis?:-damaged cells in a wound are replaced-zygote develops into a multicellular organism-identical daughter cells are produced

mitosis

Mitosis or meiosis?:-eggs formed-reduces chromosome number in daughter cells

meiosis

G1 phase

the first gap, or growth phase, of the cell cycle before DNA synthesis begins.

S phase

DNA is replicated/copied

G2 phase

the second growth phase of the cell cycle, prep for mitosis

M phase

mitosis and cytokinesis occurs (PPMAT)

mitotic spindle

a structure consisting of fibers made of microtubules and proteins that controls chromosome movement during mitosis; begins to form during prophase in the cytoplasm; assembles as other microtubules of the skeleton disassembles to provide the materials, which allows it to elongate/polymerize by incorporating more subunits of the protein tubulin (shorten/depolymerize by losing subunits)

centrosome

a subcellular region containing material that functions throughout the cell cycle to organize the cell's microtubules

centriole

structure in an animal cell that helps to organize cell division

kinetochore

a structure made up of proteins that have assembled on specific sections of DNA at each centromere

nonkinetochore microtubules

are microtubule spindles that do not attach to the centromeres chromatids, instead they overlap and push against corresponding nonkinetochore microtubules, thereby elongating the cell

prophase

(phase)-chromatin forms into chromosomes in the nucleus-centrioles begin forming spindle fibers

prometaphase

(phase)-nuclear envelope fragments, allowing chromosomes out of the nucleus-microtubules extend from centrioles and connect to the chromosome's kinetochore

metaphase

(phase)-spindle fibers made up of microtubules from each of the centrioles attach to the centromere region called the kinetochore-spindle fibers push the sister chromatids until they are all arranged in the middle-chromosomes line up on the metaphase plate

anaphase

(phase)-sister chromatids are pulled apart to opposite poles-by the end, poles have equal collection of chromosomes

telophase

(phase)-2 nuclear envelopes begin to form in each cell containing DNA-the cell is in process of elongating to separate into 2 cells

cytokinesis

(phase)-division of cytoplasm-complete division, 2 complete cells

cleavage furrow

the area of the cell membrane that pinches in and eventually separates the dividing animal cell (contractile ring)

cell plate

vesicles that form in the middle of the plant cell, which eventually grows and becomes a cell wall

binary fission

a form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size(contains an origin of replication, where chromosomes are copied, and it duplicates itself to send to the opposite side so both daughter cells contain an origin of replication)

mode of reproduction for eukaryotes?

mitosis

mode of reproduction for prokaryotes?

binary fission

shape of bacterial chromosomes in eukaryotes?

linear

shape of bacterial chromosome in prokaryotes?

circular

what controls the cell cycle?

molecules present in the cytoplasm during the S or M phase control the progression to those phases

cell cycle checkpoint

a cellular mechanism that ensures that each stage of the cell cycle is completed accurately ("go ahead" and "stop" signals for regulation)

G1 checkpoint

-makes sure there is no damage to DNA and other external factors-if conditions are not acceptable, cell cannot go to S phase, instead G0 stage-regulated by cyclin-CDK complexes

G2 checkpoint

-makes sure all DNA has been replicated-no damages to replicated DNA before entering mitosis-sufficient MPF

M phase checkpoint

-makes sure all chromosomes are properly attached to spindle at the metaphase plate before anaphase-enzyme activated (separase), allowing sister chromatids to separate and anaphase will proceed

examples of a cell that is permanently in G0 phase

muscle cells and neurons (sometimes liver cells)

G0 phase

a nondividing state occupied by cells that have left the cell cycle, sometimes reversibly

protein kinase (review)

an enzyme/protein that transfers phosphate groups from ATP to protein, phosphorylating it

cyclin + CDK

MPF (mitosis promoting factor)

MPF

a cyclin-CDK complex that triggers passage into M phase, past the G2 checkpoint; concentration depends on cyclin concentration, which means that it peaks during mitosis; needed for M phase and indirectly acts as a kinase^enough MPF? checkpoint passed

cyclin

a protein that gets its name from its cyclically fluctuating concentration in the cell; made when S phase went correctly, however it is in its inactive state

CDK

cyclin-dependent kinase; CDK + cyclin = active cyclin

growth factor

a protein released by certain cells that stimulates other cells to divide

how does PDGF (platelet-derived growth factor) stimulate fibroblast division?

fibroblasts have PDGF receptors on their plasma membranes; the binding of PDGF molecules to the receptors triggers a signal transduction pathway that allows the cell to pass the G1 checkpoint and divide

density-dependent inhibition

a phenomenon in which crowded cells stop dividing; normally divide until a single layer on a surface (ex: flask or extracellular matrix of tissue) and stops thereif cells are removed, those bordering the open space begin dividing again to fill up the gap

anchorage dependence

the requirement that a cell must be attached to a substratum (or surface, such as a flask or extracellular matrix of a tissue) in order to initiate cell division

cancerous

having traits of a tumor/cancer; uncontrolled cell division (spreading)

HeLa cells

a tumor that was removed from a woman named Henrietta Lacks; a cell line that has been reproducing and dividing in culture since 1951; ability to divide indefinitely, even without growth factors; abnormal cell cycle "immortal"

transformation

process that causes cells to behave like cancer cells (ability to divide indefinitely)

metastasis

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

benign tumor

a mass of abnormal cells with specific genetic and cellular changes such that the cells are not capable of surviving at a new site and generally remain at the site of the tumor's origin-cannot survive new site-can be removed by surgery

malignant tumor

A cancerous tumor containing cells that have significant genetic and cellular changes and are capable of invading and surviving in new sites-can survive new site-can impair the functions of one or more organs by affecting tissues and its functions-increased risk of death, due to spread

radiation (cancer treatment)

damages DNA in cancer cells (more than normal cells because cancer cells lost their ability to repair)

chemotherapy (cancer treatment)

treats known/suspected metastatic tumors with toxic drugs (to actively dividing cells), which is administered throughout the circulatory system; interferes with the steps of the cell cycle; often results in hair loss because the drugs target rapidly growing cells