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AP Biology > Cell Cycle > Flashcards

Cell Cycle 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
**cytokinesis**
- 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
cancerous cells
no contact inhibition/anchorage dependence, **divides uncontrollably** | why they can migrate or metastasize to other regions
27
contact inhibition or density-dependent inhibition
normal cells stop dividing and enter G0 as they get too crowded
28
anchorage dependence
normal cells must be anchored to surface to divide ## Footnote eg petri dish (in vitro) or extracellular membrane (in vivo)
29
**meiosis**
- 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
meiosis I
- **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
crossing-over
process by which nonsister chromatids exchange genetic material | highly organized mechanism to ensure greater variation among gametes
32
meiosis II
sister chromatids seperate into different cells | it is like mitosis
33
**Prophase I** | 1st stage of meiosis I
- 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
**Metaphase I** | 2nd stage of meiosis I
- 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
**Anaphase I** | 3rd stage of meiosis I
separation of homologous chromosomes as they are pulled by spindle fibers and migrate to opposite poles
36
**Telophase I** | 4th stage of meiosis I
homologous pairs continue to separate until they reach poles of cell | each pole has haploid number of chromosomes
37
**Cytokinesis I** | stage of meiosis I
same time as telophase I
38
**Meiosis II**
functionally the same as mitosis with same phases | chromosome number remains haploid and daughter cells same as parent cell
39
**Meiosis + Genetic Variation (3)**
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
Independent Assortment of Chromosomes
- 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
Crossover
produces **recombinant chromosomes** that combine genes inherited from both parents ## Footnote 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
random fertilization
1 human ovum/sperm = 8 mil chromosome combinations 8mil^2 recombinations
43
**cell cycle control system**
regulates rate of cell division with regular checkpoints
44
restriction point (R)
important checkpoint in the G1 phase | cell division most likely completed if it receives go-ahead
45
How is the timing of the cell cycle controlled?
initiated by growth factors and controlled by 2 molecules (cyclins and protein kinases)
46
cyclins
proteins which levels cyclically rise and fall in dividing cells (synthesized during S + G2 phase, broken down after M phase)
47
kinases
- 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
MPF
- 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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