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ISCI 350 > Cancer > Flashcards

Cancer Flashcards

1
Q

cancer

A
  • disease of the DNA where malignant cell lineages grow at the expense of surrounding tissues and, eventually, the entire organism
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2
Q

cancer development (2)

A
  • organisms have multiple controls to prevent or delay cancer
  • tumours eventually escape control by a process of evolution by NS at the cellular/tissue level
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3
Q

how are cancer cells selection for

A
  • among cancer cells, NS favours mutant cell lines that are less and less responsive to growth-controlling forces of the organism
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4
Q

cancer conflict

A
  • involved a conflict between the individual (organism) and the cell lineage (cells)
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5
Q

apoptosis (2)

A
  • cell self-sacrifice (programmed suicide)
  • involved in:
  • sculpting of organism during development
  • eliminating old, damaged, or malfunctioning cells
  • eliminating infected or malignant cells
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6
Q

cancer vs apoptosis

- cancer (3)

A
  • cell selfishness
  • favoured by cell-level selection
  • opposed by organismal-level selection
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7
Q

cancer vs apoptosis

- apoptosis (3)

A
  • cell altruism (one sacrifice for well-being of population)
  • opposed by cell-level selection
  • favoured by organismal-level selection
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8
Q

examples of conflict across levels of organization (4)

A
  • individuals in populations or in social groups
  • cells in multicellular organisms
  • organelles in cells
  • transposable elements in genomes
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9
Q

outcome of conflict between levels

A
  • compromise of selection acting at each of the levels
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10
Q

compromise of selection at different levels

A
  • depends on balance of
    1. amount of genetic variance at each level
    2. relative rate of turnover of the units at each of the levels
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11
Q

can NS happen at any level?

A
  • yes, as long as units at each level fulfill Darwin’s 4 postulates of evolution by NS (turnover, variability, heritability, differential [non-random] reproductive success)
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12
Q

examples of multilevel selection (3)

A
  • sex ratio evolution in subdivided populations (social spiders)
  • pathogen virulence
  • cancer and multicellularity
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13
Q

what proportions of males:females are expected in populations (2)

A
  • 1:1 ratio

- fisher’s sex ratio principle

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14
Q

fisher’s sex ratio principle (2)

A
  • greater reproductive success of rare sex should drive sex ratio to 1:1; 1:1 stable equilibrium ratio
  • within-group selection and the case for most species
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15
Q

social spider colonies (3)

A
  • isolated population lineages
  • 100s-1000s of colonies grow, proliferate, and go extinct with little or no mixing with one another
  • only large colonies give rise to daughter colonies
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16
Q

can biased sex ratios in social spiders be maintained by ‘group level’ selection

A

yes, Darwin’s 4 postulates apply at the colony level in social spiders

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17
Q

social spider colonies: turnover (2)

A

many colonies with high turnover:

  • 100s-1000s of colonies
  • high colony turnover
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18
Q

social spider colonies: heritability and variation (2)

A

heritable variation at the colony level:

  • colonies founded by one to a few females
  • little or no mixing (gene flow) among colony lineages
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19
Q

social spider colonies: differential (non random) reproductive success

A

colony-level advantage of overproducing females

- only large colonies give rise to daughter colonies

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20
Q

why do young social spider colonies have more femae-bias

A
  • younger colonies have had less time for within-selection to act
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21
Q

how does migration rate affect female-bias in social spider (2)

A
  • more migration = less variation between-colonies

- more migration will favour 1:1 sex ratio/within-colony selection

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22
Q

sex-ratio: when only large cells proliferate (2)

A
  • no matter the starting ratio, the ratio will tend toward a heavily female-biased ratio
  • favour between-colony selection
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23
Q

sex-ratio: all colonies are equally likely to proliferate (2)

A
  • no matter the starting ratio, the ratio will tend toward 1:1
  • favour within-colony selection
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24
Q

sex ratio: within-group selection only

A
  • 1:1 sex ratio
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25
Q

sex-ratio: between-group selection only

A
  • heavily female-biased sex ratio
26
Q

sex-ratio: within and between-group selection

A
  • balance/compromise between selective forced would lead to a equilibrium ratio between 1:1 and 1:10
27
Q

social spider selective forces

- within colonies (2)

A
  • fisher’s principle: greater reproductive success of rare sex
  • 1:1 sex ratios
28
Q

social spider selective forces

- between-colonies (2)

A
  • greater productivity of colonies

- female-biased sex ratios

29
Q

what factors determine equilibrium values (3)

A
  • migration rate
  • propagule size
  • group turnover rate
30
Q

more female-biased sex ratios evolve at: (3)

A
  • lower migration rates
  • smaller propagule size
  • greater group turnover
31
Q

propagule size

A
  • size of founding groups
32
Q

how does lower migration effect variance and proportion males (3)

A
  • lower within-group variance
  • higher between-group variance
  • lower proportion males
33
Q

how does high turnover rate effect selection and proportion males (3)

A
  • strong between-group selection
  • weaker within-group selection
  • lower proportion males
34
Q

how does low propagule size effect variance and proportion males (3)

A
  • lower within-group variance
  • higher between-group variance
  • lower proportion males
35
Q

equilibrium sex ratios

A
  • reflect a compromise between group and individual selection
36
Q

when does group level selection have the upper-hand (3)

A
  • smaller within-group variance
  • larger between-group variance
  • larger rates of turnover
37
Q

pathogen virulence: when does within-host selection predominate

A
  • high transmission and low population subdivision

- greater virulence

38
Q

pathogen virulence: when does between-host selection predominate

A
  • low transmission and high population subdivision

- lower virulence

39
Q

pathogen virulence: within-host selective forces

A
  • faster growing strains win due to higher virulence
40
Q

pathogen virulence: between-host selective forces

A
  • strains that maintain hosts alive longer win

- less virulence

41
Q

what is the trade-off between transmission and virulence

A
  • greater virulence is expected when there is greater opportunity for horizontal pathogen/parasite transmission
42
Q

virulence with horizontal transmission

A
  • more transmission -> higher pathogen virulence
43
Q

virulence with vertical transmission

A
  • less transmission -> lower pathogen virulence
44
Q

cancer: within-individual selective forces (2)

A
  • greater cell lineage proliferation

- cancer

45
Q

cancer: between-individual selective forces

A
  • greater survival of individual

- apoptosis, cancer control

46
Q

how does age affect cancer (2)

A
  • organisms with later age have more cancer as rate of turnover is very slow compared to cell turnover rate
  • selection to prevent cancer is not strong in late life
47
Q

cellular slime molds

A
  • form multicellular structures by aggregation
48
Q

cancer variance

  • variance description
  • mechanisms (2)
A

reduces variance within while maximizing variance among organisms:

  • origin from single cell
  • DNA repair, apoptosis, cell senescence
49
Q

cancer turnover

  • turnover description
  • mechanisms (2)
A

minimize within-organism turnover

  • germ-line sequestration
  • secondary somatic differentiation
  • localized cell subpopulations
50
Q

germ-line sequestration (2)

A
  • cells that give rise to gametes are set aside during early development so no mutations accumulate from additional proliferation
  • somatic cells, which arise from the zygote during mitosis, cannot get into the germ line and are genealogical dead ends
51
Q

germ-line sequestration and turnover (2)

A
  • makes germ cell turnover more equal to human turnover, especially in females
  • reduces strength of within-organism selection
52
Q

secondary somatic differentiation

- ancestral mode

A
  • cell lineage must remain mitotically active to replenish somatic lineages incapable of re-differentiation
53
Q

secondary somatic differentiation

- humans

A
  • cell lineage is released from duty of producing somatic tissues because multipotent stem cells give rise to somatic cells in different states of differentiation
54
Q

secondary somatic differentiation

- drosophilia (2)

A
  • only 13 divisions separate zygote from cells that will become gametes
  • minimizes chances of mutation
55
Q

secondary somatic differentiation

- humans

A
  • germ cells are set aside in 56-day embryo to remain sequestered for over 1-3 decades/until puberty
56
Q

compartmentalized cell subpopulations (2)

A
  • somatic cells are asexual, so cancer can only develop if multiple oncogenic mutations accumulate in the same lineage
  • it takes longer for this to happen when local populations are small or don’t persist for long; also prevents variance within the cell population
57
Q

compartmentalized cell subpopulations

- example

A
  • subpopulation structure in intestinal tissue architecture
58
Q

although organism has the upper hand, why is cancer still a possibility (2)

A
  • many generations of cell turnover involving millions of mutating cells occur in the soma
  • success of cancer control mechanisms declines as strength of organismal-level selection declines with age
59
Q

how do organisms generally delay cancer onset

A
  • gargantuan mechanism of control by the organism
60
Q

cancer: organism mechanisms of control (5)

A
  • DNA repair
  • cell-cell communication
  • oncogene suppression
  • tumour suppression by p53 and others
  • apoptosis and cell senescence
61
Q

T or F: senescence has evolved to eliminate the old and make room in population for the young (2)

A
  • false
  • unlikely that population selection is working here as Darwin’s four postulates need to be met
  • within-population selection would likely override between-population selection
62
Q

T or F: menopause evolved to protect human gene pool from spread of genetic defects (2)

A
  • false
  • unlikely that species selection is working here as Darwin’s four postulates need to be met
  • within-species selection would likely override between-species selection

ISCI 350 (14 decks)

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