Rnr 4103 Conservation Genetics: Lect 10 Inbreeding

Front 1

What are two primary genetic mechanisms that cause inbreeding depression? Which mechanism is thought to be the most common cause?

Back 1

1. increased homozygosity:
expression of a greater number of deleterious recessive alleles in inbred individuals, lowering their fitness
2. reduced heterozygosity:
reduces the fitness of inbred individuals at loci where the heterozygotes have a selective advantage over homozygotes

Front 2

Which of the two mechanisms that cause inbreeding depression does not allow for purging? Why is purging impossible at loci evolving under this mechanism?

Back 2

reduced heterozygosity:.
alleles with minor effects are unlikely to be purged selection cannot effectively target harmful alleles when they are spread across many different loci and different individuals

Front 3

How is inbreeding depression measured?

Back 3

an increase in recessive deleterious alleles

Front 4

Define heterosis. Give some examples of species for which this has occurred

Back 4

● offspring are more fit than parents
○ (genetic rescue)migrants with fresh genetic material are introduced to inbred populations,

● Several examples
–Adders
–Prairie chickens
–Drosophila
–Topminnow fish
–Florida panthers

Front 5

How does inbreeding occur in large populations?

Back 5

–Selfing ( inbreeding within local populations)
–Non-random mating e.g. proximity in trees

Front 6

How does inbreeding occur in small populations?

Back 6

–All or most individuals related
–Population of 2: after one generation, only brother-sister matings are possible

*allele frequencies in individual populations will change due to genetic drift, but average frequency over a large number of replicate populations will be unchanged
*One small population left, allele frequencies will change due to drift

Front 7

inbreeding:

Back 7

•The increase in genome-wide homozygosity caused by mating between related individuals (e.g. daughter-father, cousin-cousin); non-random mating

Front 8

inbreeding depression:

Back 8

loss of fitness (survival or reproduction) as a consequence of mating among relatives

Front 9

Which mechanism for inbreeding depression is thought to be the most common cause?

Back 9

increased homozygosity

Front 10

purging

Back 10

deleterious recessive alleles may reach substantial frequencies in large random mating populations because most copies are present in heterozygotes and therefore are not affected by natural selection