BIO220 Lecture 14 Flashcards
Genetic diversity in agricultural systems
What are the top produced & sold crops of the world?
- maize
- wheat
- rice
maize, wheat, rice account for __% of food energy intake by humans
60
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
discovered “vernalization”
Vernalization
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
biennial crops
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
- severe bottleneck
2. strong artificial selection
consequences of domestication
reduced genetic variation
ways to measure genetic variation
H: heterozygousity
P: polymorphism
pi: number of nucleotide differences per site, for any randomly sampled pair of nucleotides (genetic diversity)
how is genetic variation maintained?
BIO120??
how is genetic variation generated?
BIO120??
why do we care about genetic variation in crops?
- understand artificial selection used by our ancestors
- future improvement of crops
- pest & pathogen management
maize was domesticated from…
teosinte
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?
reduce Ne
Ne
= 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
N
= 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
effective
Why does N != Ne?
- not everyone has same number of kids
- unequal sex ratio
- overlapping generations
- fluctuations in population size
does Ne «_space;N happen in the absence of selection?
yes
