ISCI 350 > Cancer > Flashcards

Cancer Flashcards

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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
sex-ratio: between-group selection only
- heavily female-biased sex ratio
26
sex-ratio: within and between-group selection
- balance/compromise between selective forced would lead to a equilibrium ratio between 1:1 and 1:10
27
social spider selective forces | - within colonies (2)
- fisher's principle: greater reproductive success of rare sex - 1:1 sex ratios
28
social spider selective forces | - between-colonies (2)
- greater productivity of colonies | - female-biased sex ratios
29
what factors determine equilibrium values (3)
- migration rate - propagule size - group turnover rate
30
more female-biased sex ratios evolve at: (3)
- lower migration rates - smaller propagule size - greater group turnover
31
propagule size
- size of founding groups
32
how does lower migration effect variance and proportion males (3)
- lower within-group variance - higher between-group variance - lower proportion males
33
how does high turnover rate effect selection and proportion males (3)
- strong between-group selection - weaker within-group selection - lower proportion males
34
how does low propagule size effect variance and proportion males (3)
- lower within-group variance - higher between-group variance - lower proportion males
35
equilibrium sex ratios
- reflect a compromise between group and individual selection
36
when does group level selection have the upper-hand (3)
- smaller within-group variance - larger between-group variance - larger rates of turnover
37
pathogen virulence: when does within-host selection predominate
- high transmission and low population subdivision | - greater virulence
38
pathogen virulence: when does between-host selection predominate
- low transmission and high population subdivision | - lower virulence
39
pathogen virulence: within-host selective forces
- faster growing strains win due to higher virulence
40
pathogen virulence: between-host selective forces
- strains that maintain hosts alive longer win | - less virulence
41
what is the trade-off between transmission and virulence
- greater virulence is expected when there is greater opportunity for horizontal pathogen/parasite transmission
42
virulence with horizontal transmission
- more transmission -> higher pathogen virulence
43
virulence with vertical transmission
- less transmission -> lower pathogen virulence
44
cancer: within-individual selective forces (2)
- greater cell lineage proliferation | - cancer
45
cancer: between-individual selective forces
- greater survival of individual | - apoptosis, cancer control
46
how does age affect cancer (2)
- 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
cellular slime molds
- form multicellular structures by aggregation
48
cancer variance - variance description - mechanisms (2)
reduces variance within while maximizing variance among organisms: - origin from single cell - DNA repair, apoptosis, cell senescence
49
cancer turnover - turnover description - mechanisms (2)
minimize within-organism turnover - germ-line sequestration - secondary somatic differentiation - localized cell subpopulations
50
germ-line sequestration (2)
- 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
germ-line sequestration and turnover (2)
- makes germ cell turnover more equal to human turnover, especially in females - reduces strength of within-organism selection
52
secondary somatic differentiation | - ancestral mode
- cell lineage must remain mitotically active to replenish somatic lineages incapable of re-differentiation
53
secondary somatic differentiation | - humans
- 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
secondary somatic differentiation | - drosophilia (2)
- only 13 divisions separate zygote from cells that will become gametes - minimizes chances of mutation
55
secondary somatic differentiation | - humans
- germ cells are set aside in 56-day embryo to remain sequestered for over 1-3 decades/until puberty
56
compartmentalized cell subpopulations (2)
- 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
compartmentalized cell subpopulations | - example
- subpopulation structure in intestinal tissue architecture
58
although organism has the upper hand, why is cancer still a possibility (2)
- 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
how do organisms generally delay cancer onset
- gargantuan mechanism of control by the organism
60
cancer: organism mechanisms of control (5)
- DNA repair - cell-cell communication - oncogene suppression - tumour suppression by p53 and others - apoptosis and cell senescence
61
T or F: senescence has evolved to eliminate the old and make room in population for the young (2)
- 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
T or F: menopause evolved to protect human gene pool from spread of genetic defects (2)
- 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
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