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BIO220 > BIO220 Lecture 14 > Flashcards

BIO220 Lecture 14 Flashcards

Genetic diversity in agricultural systems

1
Q

What are the top produced & sold crops of the world?

A
  • maize
  • wheat
  • rice
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2
Q

maize, wheat, rice account for __% of food energy intake by humans

A

60

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3
Q

Where is the “fertile crescent”

A

near the east (between Africa & Asia)

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4
Q

What idea did Vavilov come up with?

A

Center of Origins

“Vavilov centers of diversity”

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5
Q

Center of origins / Vavilov center of diversity

A

crops originate in areas where the diversity of their wild relatives is greatest

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6
Q

Contribution from Lysenko

A

discovered “vernalization”

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7
Q

Vernalization

A

induce early flowering in biennial crops by applying cold treatment

  • flowers will delay flowering until they have experienced “winter”
  • epigenetics: methylate flowering time genes so they remember to flower early
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8
Q

biennial crops

A

flowers every other year

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9
Q

Consequence of Lysenko’s stupidity?

A
  • Lamarck > Darwin
  • train southern crops to grow in the north
  • death of evolutionary geneticists, scientists
  • catastrophic crop failures & famines
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10
Q

2 things that happen during the domestication of crops

A
  1. severe bottleneck

2. strong artificial selection

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11
Q

consequences of domestication

A

reduced genetic variation

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12
Q

ways to measure genetic variation

A

H: heterozygousity
P: polymorphism
pi: number of nucleotide differences per site, for any randomly sampled pair of nucleotides (genetic diversity)

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13
Q

how is genetic variation maintained?

A

BIO120??

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14
Q

how is genetic variation generated?

A

BIO120??

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15
Q

why do we care about genetic variation in crops?

A
  1. understand artificial selection used by our ancestors
  2. future improvement of crops
  3. pest & pathogen management
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16
Q

maize was domesticated from…

A

teosinte

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17
Q

what was demostrated by Stephen Wright’s study on maize?

A
  • there was selection
  • 43% loss of genetic variation
  • genetic diversity of teosinte vs. maize fall below the “no consequence of selection” slope
  • many used to have nucleotide differences, but not anymore due to genetic drift & bottleneck
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18
Q

what do both bottlenecks & selection do?

A

reduce Ne

19
Q

Ne

A

= effective population size
= members of the population who successfully reproduced
= size of ideal population where every adult reproduces, and genetic drift is the same as a real population

20
Q

N

A

= census size

= total number of adults in a pop’n

21
Q

rate of drift =

A

rate of decline in heterozygosity over time

22
Q

____ size is most important for evolutionary analysis

A

effective

23
Q

Why does N != Ne?

A
  • not everyone has same number of kids
  • unequal sex ratio
  • overlapping generations
  • fluctuations in population size
24
Q

does Ne &laquo_space;N happen in the absence of selection?

A

yes

25
Q

what effect does selection have on Ne?

A

make it even smaller (some will be better mates than others)

26
Q

Ne is measured as a ___ across the genome, or ____

A
  • species average

- for each gene separately

27
Q

what are the 2 views of domestication?

A
  1. bottleneck affects entire genome, and all loci are affected
  2. ^ & selection forces on certain loci reduce Ne (for those loci) in addition to the reduction felt by the entire genome
28
Q

bottlenecks have ___-wide effects on Ne

A

genome

29
Q

Artificial selection should lead to additional ___ in Ne that are ____ specific

A

reduction; locus

30
Q

how do we see if artificial selection?

A

look for genes that show evidence of a more severe bottleneck than that is typical of the rest of the genome

31
Q

How did Wright prove that artificial selection did play a part for reducing the genetic diversity of maize & teosinte?

A
  • computer simulation model: “no artificial selection”: only bottleneck
  • real data had less diversity than the simulation, so artificial selection must be present: bottleneck + further selection at certain loci
32
Q

Is there still room left for more artificial selection? (our crops already have very reduced diversity)

A

Yes, for traits with complex genetic basis

33
Q

what is the longest artificial study, and what do the results mean?

A

study: 100 generations of selection on corn kernels for protein & oil content
results: “reversal lines” when it begins to plateau show that there is still room for more selection.

34
Q

what are “reversal lines” in the 100 generation selection study?

A

When the direction of selection is reversed

35
Q

when did the Irish Potato Famine happen?

A

1845-1852

36
Q

Potatoes ……… from seed

A

do not grow easily

37
Q

Potatoes sprout easily from ____

A

underground tuber

38
Q

potatoes reproduce using…

A

clonal propagation

39
Q

Why did the Potato Famine happen?

A
  • only 1-3 genotypes
  • clonal propagation
  • no genetic diversity, so couldn’t evolve resistance
  • P. infetans (oomycete) infected potatoes
40
Q

Oomycete

A
  • fungus-like eukaryote
  • distinct from fungi
  • disperse spores by wind
41
Q

define: blight

A

plant disease, usually caused by fungi

42
Q

instead of monoculture crops, we should grow…

A

polyculture

43
Q

ignorming evolution will affect…

A
  • agriculture
  • medicine (antibiotic resistance)
  • many important social issues
44
Q

we can still use evolutionary genetics to…

A
  • discover regions of genome under past artificial selection
  • improve future crop yields
  • design sensible plant schemes to reduce risk of monoculture devastation

BIO220 (24 decks)

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