Hardy-Weinberg Equilibrium: Random Mating Flashcards
what is nonrandom mating
occurs when the probability that two individuals in a population will mate is not the same for all possible pairs of individuals.
what is random mating
probability is the same, then individuals are just as likely to mate with distant relatives as with close relatives
nonrandom mating - what form does it take
- outbreeding
- inbreeding
nonrandom mating - inbreeding
- common
- individuals are more likely to mate with close relatives (e.g. their neighbors) than with distant relatives
nonrandom mating - outbreeding
- less common than inbreeding
- individuals are more likely to mate with distant relatives than with close relatives
explain self-fertilization/selfing
most extreme version of inbreeding
self-fertilization/selfing - if an organism self-fertilizes over generations what happens to the % of heterozygous?
- inbreeding decreases frequency of heterozygotes
- increases frequency of homozygotes
- compared to HW assumptions
inbreeding - do allele frequencies change
no
inbreeding - do genotype frequencies change
- yes
- homozygotes increase in frequency
- heterozygotes decrease in frequency
does nonrandom mating cause evolution
no bc there is no change in allele frequencies
does nonrandom mating violate HW conclusions
- does not violate conclusion 1 of HW
- but it violates conclusion 2 that the population can be predicted
how is nonrandom mating like heterozygote advantage
- there is no change in allele frequencies
- but it can have profound indirect effects on evolution
what is inbreeding depression
the effect of deleterious recessive alleles on the average fitness of an offspring in the population
inbreeding depression equation
1 - (fitness of selfed) / (fitness of outcrossed)
why would inbreeding increase the effect of deleterious recessive alleles
- by increases the proportion of homozygotes
- makes it more likely to have a deleterious recessive allele
- impacts fitness: mortality rates increase
under what circumstances are we most likely to see inbreeding
- when population become very small
- the effects of genetic drift and inbreeding depression are often very important
when would we see phenotypic effects of inbreeding
- environmental stress
- later in life (maternal effects)
- inbreeding depression varies among family lineages
Florida panther example
- Panther habitat is reduced and completely isolated from other populations
- the ones that are still alive have many defects due to drift and inbreeding since the habitat is now so small
Florida panther example - what is the genetic outcome of small populations and inbreeding in the panthers
- fewer heterozygotes
- more homozygotes
Florida panther example - explain how researchers tried to help
they supplemented Florida panthers with Texas migrants
Florida panther example - did the assisted migration work
- yes, heterozygosity started increasing
- the introduced alleles from the Texas panthers caused less inbreeding
- there was a positive relationship between survival and heterozygosity
Guppy example
- guppies above waterfall had no gene flow bc it’s rare for them to get up there
- low genetic diversity and small population size creates a lot of drift and inbreeding
Guppy example - how can this be used as a model for conservation
some extinct organisms cannot be studied bc a lot of them are not available
Guppy example - what did the researchers do
they took fish that are adapted to high predation (not above the waterfall) and added them to a low predation population (above the waterfall)
Guppy example - what were the results
whether similar (low predation) or divergent (high predation) fish were introduced, the population had done better than the control (none added)
Guppy example - which population helped the original one recover most
- divergent migrants did better
- shows that you can use individuals that are more diverse and the population can still recover
