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Cell Division Flashcards

1
Q

Mitosis

A

● Produces two genetically identical daughter cells referred to as clones and preserves the chromosome number (2n)

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2
Q

Meiosis

A

● Occurs in sexually reproducing organisms and results in cells that are haploid
● Generates the genetic diversity for natural selection and evolution
● Form of cell division that produces gametes

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3
Q

Haploid

A

● Half of the chromosome number of hte parent cell

● n

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4
Q

Chromosome

A

● Consists of a highly coiled and condensed strand of DNA

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5
Q

Centromere

A

Specialized region that holds the two chromatids together

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6
Q

Kinetochore

A

A disc-shaped protein on the centromere that attaches the chromatid to the mitotic spindle during cell division

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7
Q

Cell cycle

A

● A regular sequence of growth and division that living and dividing cells pass through
● Consists of five major phases: G1, S, G2, mitosis and cytokinesis

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8
Q

Ratio of the cell volume to surface area

A

● Should be as small as possible
● The area of the cell membrane increases as the square of the radius, while the volume of the cell increases as the cube of the radius
- As a cell grows larger, the volume inside the cell increes at a faster rate than does the cell membrane

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9
Q

Capacity of the nucleus

A

● The nucleus must be able to provide enough information to produce adequate quantities of all substances to meet the cell’s needs
- Metabolically active cells are generally small
● Large, sophisticated cells like the paramecium have two nuclei that each control different cell functions

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10
Q

Interphase

A

● Inclues G1, S and G2 phases
● More than 90% of the life of a cell is spent in interphase
● Chromatin is threadlike, not condnsed

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11
Q

Cytokinesis

A

● Consists of the dividing of the cytoplasm

● Begins during mitosis, often during anaphase

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12
Q

G1 phase

A

● A period of intense growth and biochemical activity

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13
Q

S phase

A

● Stands for the synthesis or replication of DNA

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14
Q

G2 phase

A

● Cell continues to grow and to complete preparations for cell division

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15
Q

Centrosome

A

● Consists of two centrioles
● Found in the cytoplasm of an animal cell
● Duplicated during S phase

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16
Q

Microtubule organizing centers, MTOC

A

● Found in plant cells

● Serve the same functions as centrosome

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17
Q

Prophase

A

● THe nuclear membrane begins to disintegrate
● The strands of chromosomes begin to condense into discrete observable structures
● The nucleolus disappears
● in the cytoplasm, the mitotic spindle begins to form, extending from one centrosome to the other

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18
Q

Metaphase

A

● The chromosomes line up in a single file located on the equator or metaphase plate
● Centrosomes are already positioned at opposite poles of the cell
● Spindle fibers run from the centrosomes to the kinetochroes int he centromers

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19
Q

Anaphase

A

● Centromers of each chromosome separate, as spindle fibers pull apart the sister chromosomes

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20
Q

Telophase

A

● Chromosomes cluster at opposite ends of the cell, and the nuclear membrane reforms
● THe supercoiled chromosomes begin to unravel and to return to their normal, pre-cell division condition as long, threadlike strands
● Once two individual nucleoli form, mitosis is complete

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21
Q

Contact inhibition / Density-dependnet inhibition

A

● The reaction to overcrowding

● Normal cells grow and divide until they become too crowdd; then they stop dividing and enter G0

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22
Q

Anchorage dependence

A

● To divide, a cell must be attached or anchored to some surface, such as a Petri dish (in vitro) or an extracellular membrane (in vivo)

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23
Q

Cancer cells

A

● Show neither contact inhibition nor anchorage dependence
- They divide uncontrollably and do not have to be anchored to any membrane
● This is why cancer cells can migrate or metastasize to other regions of the body

24
Q

Gametes

A

● Produced through meiosis
● Ova and sperm
● THey have the haploid or monoploid chromosome number (n), half the genetic material of the parent cell

25
Meiosis I
● Reduction division | ● Process by which homologous chromosomes separate
26
Synapsis
● In Meiosis I, each chromosome first pairs up precisely with its homologue into a synaptonemal complex through the process ● Forms tetrad / bivalent
27
Crossing-over
● Process by which nonsister chromatids exchange genetic material ● Likely to occur when homologous chromosomes are aligned and binded ● Results in the recombination of genetic material ● Chiasmata are visible under microscope ● Highly organized mechanims to ensure greater variation among gametes
28
Chiasmata
● Xs on the chromsome where homolous bits of DNA are switching places
29
Meiosis II
● Similar to mitosis | ● Sister chromatids separate into different cells
30
Prophase I
● Synapsis, the pairing of homologues, occurs ● Crossing-over, the exchange of homologous bits of chromosomes, occurs ● Chiasmata, the visible manifestations of the cross-over events, are visible ● Sets the stage fore separation (segregation) of DNA
31
Metaphase I
● The homoloogu spairs of chromosomes are lined up double file along the metaphase plate ● Spindle fiers from the poles of the cell are attached to the centromers of each pair of homologues
32
Anaphase I
● Separation of homologous chromosomes as they are pulled by spindle fibers and migrate to opposite poles
33
Telophase I
● Homologous airs continue to separate until they reach the poles of hte cell - Each pole has the haploid number of chromosomes
34
Cytokinesis I
● Cytokinesis usually occurs simultaneously with telophase I
35
Indepent assortment of chromosomes
● During meiosis, homologu pairs of chromosomes separate depending on the random way in which they line up on the metaphase plate during metaphase I ● Each pair of chromosomes can line p in two possible orientations - There is a 50% chance that a particular gamete with receive a maternal chromosome
36
Cross-over (genetic variation)
● Produces recombinant chromomses that combine genes inherited from both parents ● For human, an anverage of two or three cross-over events occur in each chromosome pair ● At metaphase II, these recombinannt chromsomes line up on the metaphase plate in random fashion - Increases the possible types of gametes
37
Random fertilization
● One human ovum represents one of the approx. 8 million possible chromoosme combinations - The same is true for the human sperm ● Thus, when one sperm fertilizes one ovum, 8 million x 8 million recombinantions are possible
38
Cell cycle control system
● Regulates the rate at which cell divide | ● Seferl checkpoints exist in G1, G2, and M
39
Checkpoints
● Act as build-in stop stignals that halt the cell unless they are overridden by go-ahead signals
40
Restriction point (R)
● G1 checkpoint ● Most important one in mammals ● if it receives a go-ahead, the cell will most likely complete cell division ● If it doesn't get the appropriate signal, the cell will exit the cycle and become a nondividing cell arrested in the G0 phase
41
Protein kinases
● Common in cell signal transduction | ● Catalyze the phosphorylation of target protein that regulate hte cell cycle
42
Cyclin-dependnent kinases (CDKs)
● The rotein kinases invovled in controlling the timing o hte cell cylce ● Thye are activated by binding to the protein cyclin, which exposes the active site of the CDK and activates hte molecule ● Another example of allosteric regulation
43
Apoptosis
● A gnetically programmed series of events that result in cell death ● Cells aht are infected, damaged, or simply have come to the end of their life span die by apoptosis ● The DNA, organelles, and toher cytoplasmic components are chopped up - THe parts are packaged in vesicles that are engulfed by special scavenger cells
44
What are some examples for how the timing and rate of cell division is important?
● Bone marrow cells are always dividing in order to produce a constant supply of red and white blood cells ● Liver cells are arrested in G0 but can be induced to divie or regenerate when liver tissue is damaged ● Human intestine cells normally divide about twice per day to renew tissue destroyed during digestion ● Specialized cells, like nerve cells, do not divide at all
45
If the rate of cell division is not controlled, it can result in what?
Uncontrolled cell divivion, characteristic of cancer
46
What are the two important factors that imit cell size and promote cell division?
● Ratio of the volume of a cell to the surface area | ● Capacity of the nucleus to control the entire cell
47
Why does the ratio of V to SA determine when the cell divides?
● A cell depends on the cell membrane for exchange of nutrients and waste products ● A cell's volume is proportional to the amount of nutrients it needs
48
How is cytoinesis done in animal cells?
● A cleavage furrow forms down the middle of hte cell | ● Actin and myosin microfilaments pinch in the cytoplasm
49
How is cytokinesis done in plant cells?
● A cell plate forms during telophase as vesicles from the Golgi coalesce down the middle of the cell ● Daughter plant cells do not separate from each other ● A new cell wall forms, and a sticky middle lamella cements adjacent cells together
50
How does meiosis result in genetic diversity?
● Genetic material is randomly separated and recombined so that each gamete differs genetically from every other gamete
51
What are the three tyeps of genetic variaiton result from the processes of meiosis and fertilization?
● Independnet assortment of chromosomes ● Crossing-over ● Random fertilization of an ovum by a sperm
52
What is timing of the cell cycle controlled by?
● It is initiated by growht factors | ● Controlled by two kinds of molecules, cyclins and protein kinases
53
How do many CDKs regulate the cell cycle at specific stages?
● Each CDK is activated by its own cyclin ● Cyclin is manufactured only at the rihgt time ● After the CDK acts, its cyclin is broken down by a protease ● Cyclins are synthesized in response to various molecular signals, including growth factors
54
What is an overview of the chain reaction that controls the cell cycle?
Growth factor -> Cyclin synthesis -> CDK activation -> Cell cycle evvent
55
Why do human cells carry out apoptosis?
● During embryonic development when cells or tissues are no longer needed, they die and are engulfed by neighboring cells ● The cell has sustained too much genetic damage that could lead to cancer - This is common for epithelial cells on the surface of the skin, which have been exposed to extensive solar radiation ● In mammals, including humans, several different pathways invovling enzymes called caspases carry out apoptosis - Signals from differnet sources trigger the apoptosis pathway, inside or outside the cell
56
Why do plant cells carry out apoptosis?
● In plant cells, apoptosis is an important defense against infection by fungus and bacterium - By dying, cells at the site of infection leave no living tissue to spread infection inside the plant
57
What suggests that the mechanism for apoptosis evolved early in the evolution?
● The mechanism of apoptosis is basically similar in single-celled yeast, and in mammalian cells

AP Biology (15 decks)

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