13.1
What is meant by the term "inbreeding" and why is it important to define the term
“inbreeding” when using it?
13.2
In what sense are we all inbred?
13.3
Explain how inbreeding occurs even in random mating populations.
13.4 How can an individual that is autozygous (IBD) be heterozygous?
13.5 Identify all inbred individuals in Figure 13.5 and calculate their inbreeding coefficients.
13.6.
How is inbreeding depression measured?
13.7 We saw in Example 13.1 that there was a 66% mean reduction in fitness as measured by seed production in two populations of monkeyflowers (
δ
= 0.665). How many lethal equivalents are there per diploid individual in these populations? How does this compare to the amount of inbreeding depression estimated in mammals?
13.8 What are the two primary genetic mechanisms that cause inbreeding depression? Which mechanism is thought be the most common cause inbreeding depression?
13.9 What is meant by the term “purging”?
13.10 Which of the two mechanisms that cause inbreeding depression does not allow for purging? Why is purging impossible at loci resposnbile for inbreeding depression under this mechanism?
13.11
Why are mildly-deleterious alleles difficult to purge (Hint: why are lethal alleles easily purged)?
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13.12
The pedigree below is from a song sparrow population on Mandarte Island in western
Canada (Guest Box 13). Identify all inbred individuals in the pedigree below (Keller and Waller
2002) and calculate their inbreeding coefficients.
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13.13 The following pedigree appeared in one of the original papers on inbreeding (Wright
1923). Calculate the inbreeding coefficient for Favourite 252, the foundation bull for all
Shorthorn cattle. Notes: (1) the upper parent in each case is the bull and the lower parent is the cow; (2) Studley Bull 626 is sometimes listed just as 626.
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13.14 Assume that individuals F1-F4 below are the founders of a captive breeding program for larlarlongs, an extraterrestrial species native to the planet Tralfalmadore. Use coin-flips to derive one possible outcome of a gene-drop analysis for this pedigree. Assume that individuals A-D are the only surviving larlarlongs in the universe. What are the allele frequencies for individuals A-
D based upon the outcome of your single gene-drop? What are the observed and expected heterozygosities for individuals A-D based upon the outcome of your single gene-drop? If you performed 10,000 such gene drops, what do you think the average observed heterozygosity would be for individuals A-D? How many of the eight original alleles remain in the captive population of larlarlongs based upon your single gene drop outcome?
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13.15
Wolves in Sweden have been naturally recovering from near-extinction for the past three decades (Chapron et al. 2013). All 250 wolves in Sweden descend from only 5 founders, and reducing the inbreeding coefficient has become the main policy target. Inbreeding levels are high among living wolves; on average individuals are more related to each other than siblings. In
2010 the average coefficient of inbreeding ( F ) was 0.27 (Laikre et al. 2013).
Wolf recovery is controversial, and vocal interest groups have been calling to reduce population size because of harmful effects on hunting and farming. Under pressure from these groups,
Swedish authorities recently opened a wolf hunt, which selectively targets the most inbred wolves. This hunt is presented as a conservation action under the reasoning that removing some of the most inbred wolves is “the only measure in the short term that can reduce inbreeding”, and thus a step toward the species being able to maintain itself on a long-term basis.
Do you think such a wolf hunt will be effective in reducing harmful effects of genetic drift and inbreeding in this population?
What actions do you think should be considered to reduce the harmful effects of genetic drift and inbreeding in this population?
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