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AP Biology > Cell Cycle > Flashcards

Cell Cycle Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

cell division is used for (3)

A

growth, repair, and reproduction

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2
Q

2 types of cell division

A

mitosis and meiosis

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3
Q

mitosis

A
  • produces 2 genetically identical daughter cells (clones)
  • preserves the diploid (2n) chromosome number
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4
Q

meiosis

A
  • occurs in sexually reproducing organisms, results in cells that are haploid
  • half the chromosome number of the parent cell
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5
Q

structure of a chromosome

A

highly coiled/condensed strand of DNA

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6
Q

replicated chromosome

A

consists of 2 sister chromatids (exact copies of each other)

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7
Q

centromere

A

specialized region that holds 2 chromatids together

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8
Q

kinetochore

A

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

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9
Q

cell cycle

A

complex sequence of growth and division of cells

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10
Q

What is the frequency of cell division?

A

varies with cell type, but tightly regulated by complex mechanism involving kinases and allosteric interaction

  • bone marrow cells always dividing in order to produce constant supply of blood cells
  • liver cells arrested in G0 (stopped dividing) but can be induced to divide/regenerate when liver tissue is damaged
  • human intestine cells normally divide 2 times a day to renew damaged tissue during digestion
  • nerve cells do not divide at all
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11
Q

Frequency of cell division?

A

varies with cell type

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12
Q

2 factors that limits cell size and promote cell division

A

ratio of volume of cell to surface area + capacity of nucleus to control entire cell

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13
Q

How does ratio of cell volume to surface area affect cell division?

A

when cell grows: surface area of cell membrane increases as the square of the radius and volume increases as the cube of the radius

= volume increases at faster rate than cell membrane

ratio is major factor of cell division

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14
Q

How does the capacity of the nucleus affect cell division?

A

nucleus must be able to provide enough info and substances to meet cell’s needs

  • metabolically active cells generally small
  • larger cells have evolved to exist with multiple nuclei
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15
Q

5 major phases of the cell cycle

A

interphase (G1, S, G2), mitosis, cytokinesis

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16
Q

interphase

A

more than 90% of cell’s life, chromatin is threadlike and not condensed

1 nucleus, 1 centrosome or MTOC

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17
Q

G1 (Gap 1) phase

during interphase

A

period of intense growth and biochemical activity

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18
Q

S (synthesis) phase

during interphase

A

synthesis or replication of DNA

centrosome is duplicated

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19
Q

G2 (Gap 2) phase

A

cell continues to grow and complete preparation for cell division

centrosomes will seperate and move to opposite poles

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20
Q

mitosis

A

actual dividing of the nucleus
prophase, metaphase, anaphase, telophase

21
Q

prophase (4)

1st phase of mitosis

A
  • nuclear membrane begins to disintegrate
  • chromosome strands condense (X)
  • nucleolus disappears
  • mitotic spindle begins to form, from each centrosome
22
Q

metaphase (3)

2nd phase of mitosis

A
  • chromosomes line up in single file on equator (metaphase plate)
  • centrosomes positioned at opposite poles
  • spindle fibers run from centrosomes to kinetochores in centromeres
23
Q

anaphase

3rd phase of mitosis

A
  • centromeres of each chromosome separate, spindle fibers pull apart sister chromosomes
24
Q

telophase

4th phase of mitosis

A
  • chromosomes cluster at opposite ends, and nuclear membrane reforms
  • supercoiled chromosomes unravel and return to normal threadlike strands
  • mitosis complete after 2 nucleoli form
25
Q

cytokinesis

A
  • dividing of cytoplasm
  • begins during anaphase
  • animal cells: cleavage furrow forms down middle as actin and myosin microfilaments pinch in cytoplasm
  • plant cell: cell plate forms during telophase as vesicles from Golgi merge down middle, daughter plant cells do not seperate but new wall forms and middle lamella joins adjacent cells together
26
Q

cancerous cells

A

no contact inhibition/anchorage dependence, divides uncontrollably

why they can migrate or metastasize to other regions

27
Q

contact inhibition
or density-dependent inhibition

A

normal cells stop dividing and enter G0 as they get too crowded

28
Q

anchorage dependence

A

normal cells must be anchored to surface to divide

eg petri dish (in vitro) or extracellular membrane (in vivo)

29
Q

meiosis

A
  • generates genetic diversity for natural selection + evolution
  • produces gametes (ova/sperm), which have haploid/monoploid chromosome number (n), half the genetic material of parent cell
  • nucleus divides twice
  • every gamete is different
  • sexual reprodution involves fusion of 2 haploid gametes and restores diploid chromosome number to offspring
30
Q

meiosis I

A
  • reduction division
  • homologous chromosomes seperate
  • each chromosome first pairs up precisely with homologue into synaptonemal copmlex by synapsis, forming tetrad/bivalent structure
  • pairing process causes crossing-over
31
Q

crossing-over

A

process by which nonsister chromatids exchange genetic material

highly organized mechanism to ensure greater variation among gametes

32
Q

meiosis II

A

sister chromatids seperate into different cells

it is like mitosis

33
Q

Prophase I

1st stage of meiosis I

A
  • synapsis (pairing of homologues)
  • crossing-over (exchange of homologous bits of chromosomes
  • chiasmata (visible manifestation of crossover events)
  • sets stage for separation of DNA
34
Q

Metaphase I

2nd stage of meiosis I

A
  • homologous pairs of chromosomes are lined up double file along metaphase plate
  • spindle fibers from poles attached to centromeres of each pair of homologues
35
Q

Anaphase I

3rd stage of meiosis I

A

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

36
Q

Telophase I

4th stage of meiosis I

A

homologous pairs continue to separate until they reach poles of cell

each pole has haploid number of chromosomes

37
Q

Cytokinesis I

stage of meiosis I

A

same time as telophase I

38
Q

Meiosis II

A

functionally the same as mitosis with same phases

chromosome number remains haploid and daughter cells same as parent cell

39
Q

Meiosis + Genetic Variation (3)

A

3 types of genetic variation from meiosis and fertilization
1. independent assortment of chromosomes
2. crossing-over
3. random fertiliation of ovum by sperm

40
Q

Independent Assortment of Chromosomes

A
  • homologous pairs of chromosomes separate depending on random way they line up on metaphase palte
  • each pair can line up in 2 ways
  • gamete has 50% chance of receiving maternal chromosome, 50% chance of paternal chromosome

23 pairs of chromosomes in humans = 2^23 (8 mil) combinations

41
Q

Crossover

A

produces recombinant chromosomes that combine genes inherited from both parents

human: average of 2 or 3 crossover events occur in each chromosome pair, recombinant chromosomes then line up on metaphase palte in random fashion (more possibilities of gametes)

42
Q

random fertilization

A

1 human ovum/sperm = 8 mil chromosome combinations
8mil^2 recombinations

43
Q

cell cycle control system

A

regulates rate of cell division with regular checkpoints

44
Q

restriction point (R)

A

important checkpoint in the G1 phase

cell division most likely completed if it receives go-ahead

45
Q

How is the timing of the cell cycle controlled?

A

initiated by growth factors and controlled by 2 molecules (cyclins and protein kinases)

46
Q

cyclins

A

proteins which levels cyclically rise and fall in dividing cells (synthesized during S + G2 phase, broken down after M phase)

47
Q

kinases

A
  • ubiquitous class of proteins that activate other proteins by phosphorylating them
  • kinases in cell cycle activated when they bind to cyclin (cyclin-dependent kinases/Cdks)
  • Cdk binds to cyclin = cyclin-Cdk complex
48
Q

MPF

A
  • type of cyclin-Cdk complex
  • triggers cell’s passage from G2 to M
  • maturation promoting factor
  • contributes to chromosome condensation and spindle formation
  • during anaphase (after M phase), switches off by breaking down cyclin, Cdk persists in cell in inactive form until it becomes part of MPF again

AP Biology (14 decks)

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