Hardy-Weinberg Equilibrium: Random Mating

Question 1

what is nonrandom mating

Answer 1

occurs when the probability that two individuals in a population will mate is not the same for all possible pairs of individuals.

Question 2

what is random mating

Answer 2

probability is the same, then individuals are just as likely to mate with distant relatives as with close relatives

Question 3

nonrandom mating - what form does it take

Answer 3

• outbreeding
• inbreeding

Question 4

nonrandom mating - inbreeding

Answer 4

• common
• individuals are more likely to mate with close relatives (e.g. their neighbors) than with distant relatives

Question 5

nonrandom mating - outbreeding

Answer 5

• less common than inbreeding
• individuals are more likely to mate with distant relatives than with close relatives

Question 6

explain self-fertilization/selfing

Answer 6

most extreme version of inbreeding

Question 7

self-fertilization/selfing - if an organism self-fertilizes over generations what happens to the % of heterozygous?

Answer 7

• inbreeding decreases frequency of heterozygotes
• increases frequency of homozygotes
• compared to HW assumptions

Question 8

inbreeding - do allele frequencies change

Answer 8

no

Question 9

inbreeding - do genotype frequencies change

Answer 9

• yes
• homozygotes increase in frequency
• heterozygotes decrease in frequency

Question 10

does nonrandom mating cause evolution

Answer 10

no bc there is no change in allele frequencies

Question 11

does nonrandom mating violate HW conclusions

Answer 11

• does not violate conclusion 1 of HW
• but it violates conclusion 2 that the population can be predicted

Question 12

how is nonrandom mating like heterozygote advantage

Answer 12

• there is no change in allele frequencies
• but it can have profound indirect effects on evolution

Question 13

what is inbreeding depression

Answer 13

the effect of deleterious recessive alleles on the average fitness of an offspring in the population

Question 14

inbreeding depression equation

Answer 14

1 - (fitness of selfed) / (fitness of outcrossed)

Question 15

why would inbreeding increase the effect of deleterious recessive alleles

Answer 15

• by increases the proportion of homozygotes
• makes it more likely to have a deleterious recessive allele
• impacts fitness: mortality rates increase

Question 16

under what circumstances are we most likely to see inbreeding

Answer 16

• when population become very small
• the effects of genetic drift and inbreeding depression are often very important

Question 17

when would we see phenotypic effects of inbreeding

Answer 17

• environmental stress
• later in life (maternal effects)
• inbreeding depression varies among family lineages

Question 18

Florida panther example

Answer 18

• 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

Question 19

Florida panther example - what is the genetic outcome of small populations and inbreeding in the panthers

Answer 19

• fewer heterozygotes
• more homozygotes

Question 20

Florida panther example - explain how researchers tried to help

Answer 20

they supplemented Florida panthers with Texas migrants

Question 21

Florida panther example - did the assisted migration work

Answer 21

• yes, heterozygosity started increasing
• the introduced alleles from the Texas panthers caused less inbreeding
• there was a positive relationship between survival and heterozygosity

Question 22

Guppy example

Answer 22

• 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

Question 23

Guppy example - how can this be used as a model for conservation

Answer 23

some extinct organisms cannot be studied bc a lot of them are not available

Question 24

Guppy example - what did the researchers do

Answer 24

they took fish that are adapted to high predation (not above the waterfall) and added them to a low predation population (above the waterfall)

Question 25

Guppy example - what were the results

Answer 25

whether similar (low predation) or divergent (high predation) fish were introduced, the population had done better than the control (none added)

Question 26

Guppy example - which population helped the original one recover most

Answer 26

• divergent migrants did better
• shows that you can use individuals that are more diverse and the population can still recover