Chapter 11 Flashcards
What is the genetic load?
J. Crow defined it as the average decline in fitness as related to max fitness.
What is inbreeding?
When individuals who are related to each other mate. Can result in an excess of homozygotes and population sub-structuring.
How does inbreeding occur?
From assortive mating (mating with like types), consanguinity (mating with relatives), or small population size (mating with relatives by chance).
What is caused by inbreeding?
Inbred wolves on Isle Royal have spinal malformations…inbreeding effects can accumulate over time.
What is the inbreeding coefficient?
It reflects the possibility that 2 alleles are identical by descent.
Why is inbreeding bad?
It exposes rare deleterious recessive alleles as homozygotes.
How do we calculate F?
Tracing relationships thru a pedigree, looking at among-pop differentiation f-st, or looking at the deficit of het’s relative to HW ( F= 1- hetobs/hetexp).
What are short-term, medium, and long term effects of inbreeding?
Inbreeding depression for short term, deleterious allele fixing for medium term, and loss of genetic diversity, effective population size, and the potential for mutational meltdown in the long term.
How can we infer the past from genomic structures?
Time since divergence, was the evolution adaptive or non adaptive, etc etc.
What is balancing selection?
Selection that acts to favor both or all alleles at a locus. It is a powerful force that retains genetic variation. It can act by favoring rare genotypes or alleles, like 50:50 sex ration, right or left handed cichlid fish, etc.
What is Fjk?
The probability that an allele sampled at a locus in one individual is ibd with an allele sampled from the same locus in the other individual.
How does inbreeding affect homozygosity?
It increases homozygotes while decreasing the frequency of heterozygotes.
What are consequences of inbreeding?
Homozygosity and gene identity (ibd) increase.
Variance among families and lines increases, but decreases within lines.
Possible loss of lines and families.
Inbreeding depression, or decline in fitness.
What are mechanisms of inbreeding depression?
Can result from:
- dominance (mostly recessive deleterious alleles becoming exposed)
- overdominance (heterozygotes simply superior to both homozygotes)
How is population sub-structure involved in inbreeding?
When pops are subdivieded into isolated groups, inbreeding can occur from genetic drift.
This is pronounced in small or ancient isolated populations.
This occurs even if random mating is occuring! Causes an apparent deficiency in the population as a whole.
