cell growth, cell cycle, mitosis and cytokinesis

in unicellular organisms, division of one cell reproduces the …

entire organism

multicellular eukaryotes depend on cell division for…

1. development from a fertilized egg

2. growth

3. repair

cell division is an integral part of the …

cell cycle (the life of a cell from formation to its own division)

most cell division results in …

two daughter cells with identical genetic information, DNA

what is the exception to the fact that most cell division results in two daughter cells with identical genetic information

meiosis, special type of division that can produce sperm and egg cells

all the DNA in a cell constitutes the cell’s …

genome

DNA molecules in a cell are package into …

chromosomes

eukaryotic chromosomes consist of …

chromatin

what is chromatin

complex of DNA and protein that condenses during cell division

… cells have two sets of chromosomes

somatic (non-reproductive cells)

… have half as many chromosomes as somatic cells

reproductive cells (sperm and eggs)

in preparation for cell division…

DNA is replicated and the chromosomes condense

each duplicated chromosomes has two…

sister chromatids (joined copies of the original chromosome)

what is the centromere

the narrow “waist” of the duplicated chromosome, where the two chromatids are most closely attached

during cell division, the two sister chromatids of each duplicated chromosome…

separate and move into two nuclei

once separated, the chromatids are called…

chromosomes

eukaryotic cell division consists of…. (2 types of division)

karyokinesis (division of genetic material)

cytokinesis (division of cytoplasm)

the cell cycle consists two main phases…

1. mitotic (M) phase= mitosis and cytokinesis

2. interphase= cell growth and copying of chromosomes in preparation for cell division

interphase makes up around… of the cell cycle

90%

what are the three phases of interphase

1. G1 phase= first gap

2. S phase= synthesis (CHROMOSOMES DUPLICATED)

3. G2 phase= second gap

mitosis is broken down into four stages

prophase

metaphase

anaphase

telophase

before mitosis happen… what happens in G2 phase of interphase?

centrioles duplicate and begin moving to opposite poles of the cell

outline what happens during prophase

1. chromosomes condense

2. nuclear envelope begins to dissolve

3. early mitotic spindle begins to form

outline what happens during metaphase

4. chromosomes line up along metaphase plate in the center of the cell

5. mitotic spindle is fully formed

6. microtubules connect to kinetochore, the constricted middle of the chromosome

outline what happens in anaphase

7. spindle microtubules pull apart the duplicated chromosomes

8. chromosomes move to opposite poles of the cell

9. the sister chromatids are now properly called daughter chromosomes

outline what happens during telophase

10. chromosomes uncondense

11. nuclear envelope reforms

12. spindle microtubules are disassembled

13. cytokenesis occurs (division of the cytoplasm via a cleavage furrow

what means that plate cells cannot “pinch” in two in plant cells

cell wall

what forms in the middle of the two plant cells and grows outward

cell plate

the frequency of cell division varies with the type of cell, these differences result from …

regulation at the molecular level

… cells manage to escape the usual controls of the cell cycle

cancer

the sequential events of the cell cycle are directed by a distinct…

cell cycle control system (comparable to a clock)

the cell cycle control system is regulated by both… and … controls

internal and external

the cell cycle control system has specific … where the cell cycle stops until a go-ahead signal is received

checkpoints

where are the three important checkpoints

G1, G2 and M phase

what checkpoint seems to be the most important

G1 checkpoint

why is the G1 checkpoint most important

if the cell receives the go ahead signal at the G1 checkpoint, it will usually complete the S, G2, and M phases and divide

what happens if the cell does not receive the go-ahead signal at the G1 checkpoint

it will exit the cycle, switching into a nondividing state called the G0 phase

explain the function of the M checkpoint

cells will not begin anaphase until all the chromosomes are properly attached to the spindle at the metaphase plate

this mechanism ensures that daughter cells have the correct number of chromosomes

external factors that influence cell division include specific …

growth factors

growth factors are …

released by certain cells and stimulate other cells to divide

… is made by blood cell fragments called platelets

platelet-derived growth factor

in density-dependent inhibition…

crowded cells will stop dividing

cancer cells do not need growth factors to grow and divide…

• they make their own growth factor

• they may convey a growth factor’s signal without the presence of the growth factor

• they may have an abnormal cell cycle control system

cell that acquire the ability to divide indefinitely are undergoing…

transformation

if abnormal cells remain only at the original site, the lump is called a .. tumor

benign

… tumors invade surrounding tissues and undergo metastasis

malignant

define metastasis

the spread of cancer cells to other parts of the body, where they may form additional tumors