Flashcards in BIO220 Lecture 14 Deck (44):
What are the top produced & sold crops of the world?
maize, wheat, rice account for __% of food energy intake by humans
Where is the "fertile crescent"
near the east (between Africa & Asia)
What idea did Vavilov come up with?
Center of Origins
"Vavilov centers of diversity"
Center of origins / Vavilov center of diversity
crops originate in areas where the diversity of their wild relatives is greatest
Contribution from Lysenko
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
flowers every other year
Consequence of Lysenko's stupidity?
- Lamarck > Darwin
- train southern crops to grow in the north
- death of evolutionary geneticists, scientists
- catastrophic crop failures & famines
2 things that happen during the domestication of crops
1. severe bottleneck
2. strong artificial selection
consequences of domestication
reduced genetic variation
ways to measure genetic variation
pi: number of nucleotide differences per site, for any randomly sampled pair of nucleotides (genetic diversity)
how is genetic variation maintained?
how is genetic variation generated?
why do we care about genetic variation in crops?
1. understand artificial selection used by our ancestors
2. future improvement of crops
3. pest & pathogen management
maize was domesticated from...
what was demostrated by Stephen Wright's study on maize?
- 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
what do both bottlenecks & selection do?
= 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
= census size
= total number of adults in a pop'n
rate of drift =
rate of decline in heterozygosity over time
____ size is most important for evolutionary analysis
Why does N != Ne?
- not everyone has same number of kids
- unequal sex ratio
- overlapping generations
- fluctuations in population size
does Ne << N happen in the absence of selection?
what effect does selection have on Ne?
make it even smaller (some will be better mates than others)
Ne is measured as a ___ across the genome, or ____
- species average
- for each gene separately
what are the 2 views of domestication?
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
bottlenecks have ___-wide effects on Ne
Artificial selection should lead to additional ___ in Ne that are ____ specific
how do we see if artificial selection?
look for genes that show evidence of a more severe bottleneck than that is typical of the rest of the genome
How did Wright prove that artificial selection did play a part for reducing the genetic diversity of maize & teosinte?
- 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
Is there still room left for more artificial selection? (our crops already have very reduced diversity)
Yes, for traits with complex genetic basis
what is the longest artificial study, and what do the results mean?
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.
what are "reversal lines" in the 100 generation selection study?
When the direction of selection is reversed
when did the Irish Potato Famine happen?
Potatoes ......... from seed
do not grow easily
Potatoes sprout easily from ____
potatoes reproduce using...
Why did the Potato Famine happen?
- only 1-3 genotypes
- clonal propagation
- no genetic diversity, so couldn't evolve resistance
- P. infetans (oomycete) infected potatoes
- fungus-like eukaryote
- distinct from fungi
- disperse spores by wind
plant disease, usually caused by fungi
instead of monoculture crops, we should grow...
ignorming evolution will affect...
- medicine (antibiotic resistance)
- many important social issues