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Flashcards in G18 Deck (21):

what is the inbreeding coefficient



what are the two major genetic consequences of inbreeding

1. alters genotype frequency NOT ALLELE FREQUENCY
2. Reduced effective recombination


what happens to heterozygosity in selfing plants

heteros mate with self = 50% hetero , 50 homo
homos mate = 100% homo


what is an allozygous homozygote

homozygous but both alleles come from a different individual


what is an autozygous homozygote

both alleles are identical by descent


what is the probability of autozygosity

A = common ancestor
i = number of individuals in path


what are the benefits of inbreeding

reproductive assurance
increased gene transmission


give an example of reproductive assurance

e.g haplodiploidy insects: solitary females can produce sons to mate with and produce diploid daughter


give an example of increased gene transmission

self compatible plants have 50% adv if cost of producing selfing pollen dfoesnt affect quantity of outbreeding pollen


how can inbreeding be increased

by structural changes (eg. in plants)
due to offspring mating/dispersal patterns


give an example of strucutral changes which increase inbreeding

reduction of sexual adaptations eg.g cleistogamous flowers produce buds that dont open


give an example of increased inbreeding due to offspring mating/dispersal patterns

Sex ratio bias and haplodiploidy in parasitc hymenoptera and mites, females should produce 1:1 sex ratio in offspring, but not if offspring hatch adn mate before dispersing.
extreme example: mite acarophenax 1 son to 15 daughters


what is inbreeding depression

relative decrease in fitness of inbred progeny compared to non inbred progeny (cumulative)


give ane example of inbreeding depression

nestling mortality rate in inbred pairs of great tits


what are the two hypothesis for the causes of inbreeding depression

1. overdominance hypothesis: genome wide heterozygosity is advantageous and this is reduced by inbreeding
2. dominance hypothesis: unmasking of deleterious recessives


what is purging of deleterious recessives

when invreeding depression leads to an inital decrease in population fitness, but population may recover to some extent if not fully if the deleterious alleles are selected against (purged)


give an example of purging deleterious recessives

chillingham cattle
isolated for 300 years
underwent a population crash to 5 bulls and 8 cows
now back to 91 but very homozygous, with no reduction in fertility or viability.
pruging effect is also significant for inbred sumatran tigers in zoos


give to examples of plants promoting outbreeding

monecious plants: heterostyl- plants may ahve male and female acting flowers at different times (protogyny and protoandry)
Dioecious plants: sexes on different plants. eg male and female holly


what is an example of a molecular adaptation promiting oubreeding

multi alleleic incompatibiltiy systems
eg. plant has S1S2 aleles only pollen with different s allels grow down stigma.
common in plants ciliate, basidommycetes and slime moulds


what are some examples of behavioural adaptations promoting outbreeding

kin recognition in social animals
young females dont come into breeding condition if father is dominant eg. black tailed prarie dog
striped mouse: presence of male accelerates juvenile female growth rates but not if caged with father


give an example of optimal levels of outbreeding

delphinium flower, found outbreeding increased fittness until 10m distance when it began to decrease with distance.