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AP Biology > Cell Division > Flashcards

Cell Division Flashcards

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AP® Biology flashcards Biology 101 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
Q

Meiosis I

A

● Reduction division

● Process by which homologous chromosomes separate

26
Q

Synapsis

A

● In Meiosis I, each chromosome first pairs up precisely with its homologue into a synaptonemal complex through the process
● Forms tetrad / bivalent

27
Q

Crossing-over

A

● 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
Q

Chiasmata

A

● Xs on the chromsome where homolous bits of DNA are switching places

29
Q

Meiosis II

A

● Similar to mitosis

● Sister chromatids separate into different cells

30
Q

Prophase I

A

● 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
Q

Metaphase I

A

● 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
Q

Anaphase I

A

● Separation of homologous chromosomes as they are pulled by spindle fibers and migrate to opposite poles

33
Q

Telophase I

A

● Homologous airs continue to separate until they reach the poles of hte cell
- Each pole has the haploid number of chromosomes

34
Q

Cytokinesis I

A

● Cytokinesis usually occurs simultaneously with telophase I

35
Q

Indepent assortment of chromosomes

A

● 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
Q

Cross-over (genetic variation)

A

● 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
Q

Random fertilization

A

● 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
Q

Cell cycle control system

A

● Regulates the rate at which cell divide

● Seferl checkpoints exist in G1, G2, and M

39
Q

Checkpoints

A

● Act as build-in stop stignals that halt the cell unless they are overridden by go-ahead signals

40
Q

Restriction point (R)

A

● 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
Q

Protein kinases

A

● Common in cell signal transduction

● Catalyze the phosphorylation of target protein that regulate hte cell cycle

42
Q

Cyclin-dependnent kinases (CDKs)

A

● 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
Q

Apoptosis

A

● 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
Q

What are some examples for how the timing and rate of cell division is important?

A

● 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
Q

If the rate of cell division is not controlled, it can result in what?

A

Uncontrolled cell divivion, characteristic of cancer

46
Q

What are the two important factors that imit cell size and promote cell division?

A

● Ratio of the volume of a cell to the surface area

● Capacity of the nucleus to control the entire cell

47
Q

Why does the ratio of V to SA determine when the cell divides?

A

● 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
Q

How is cytoinesis done in animal cells?

A

● A cleavage furrow forms down the middle of hte cell

● Actin and myosin microfilaments pinch in the cytoplasm

49
Q

How is cytokinesis done in plant cells?

A

● 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
Q

How does meiosis result in genetic diversity?

A

● Genetic material is randomly separated and recombined so that each gamete differs genetically from every other gamete

51
Q

What are the three tyeps of genetic variaiton result from the processes of meiosis and fertilization?

A

● Independnet assortment of chromosomes
● Crossing-over
● Random fertilization of an ovum by a sperm

52
Q

What is timing of the cell cycle controlled by?

A

● It is initiated by growht factors

● Controlled by two kinds of molecules, cyclins and protein kinases

53
Q

How do many CDKs regulate the cell cycle at specific stages?

A

● 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
Q

What is an overview of the chain reaction that controls the cell cycle?

A

Growth factor -> Cyclin synthesis -> CDK activation -> Cell cycle evvent

55
Q

Why do human cells carry out apoptosis?

A

● 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
Q

Why do plant cells carry out apoptosis?

A

● 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
Q

What suggests that the mechanism for apoptosis evolved early in the evolution?

A

● The mechanism of apoptosis is basically similar in single-celled yeast, and in mammalian cells

AP Biology (15 decks)

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