Week 11 Flashcards
Describe two phenomena that can lead to genetic correlations.
(1) Pleiotropy– phenotypic effect of a gene on >1 phenotypic character
(2) Linkage disequilibrium– non-random association of >/= 2 alleles at >/= 2 loci
How do you calculate a response to selection using the multivariate breeders’ equation?
Delta z = G[beta]
where
delta z is the vector of changes in mean trait values and
B (beta) is the vector of selection gradients
G is the G matrix or matrix of genetic variances and covariances among phenotypic traits
** Review slide Week 11 Concluding Phylogeny
How do you calculate the coefficient of linkage disequilibrium (LD)?
D= (g11g22)-(g12g21)
Multiplying the frequencies of all gamete types
- see slide for clarification
Define and give examples of life history traits.
Age-specific probabilities of survival and reproduction in a population
Seeks answers to such questions as:
(1) Why do some organisms mature earlier versus late?
(2) Why do some organisms have many versus few offspring?
(3) Why do some organisms have long versus short lives?
Examples of life history traits:
- Lifespan (annual vs perennial plants)
- Offspring number (frog vs whale)
- Offspring size (kiwi egg vs kangaroo joey)
- Generation time (periodic cicada vs aphids)
- Breeding events
What are the possible causes of LD?
(1) Non-random mating
(2) New mutation
(3) Union of two populations
(4) Low/negligible recombination
(5) Genetic Drift
(6) Natural Selection
Define and compare semelparity and iteroparity.
Semelparity: reproductive strategy in which an organism produces all of its offspring in a single event
Iteroparity: reproductive strategy in which an organism produces offspring across multiple events
Age-specific patterns of survival and reproduction in a population are depicted in a life table.
Explain the structure of a life table.
lx- probability of survival to age x
mx- average fecundity (number of eggs/newborns/seeds produced at age x)
Sumlxmx= R: the growth rate of the genotype
(each female, on average, produces 4 offspring)
Increasing lx (up to and including the age of last reproduction) should increase fitness.
Why should early reproduction should be selected for?
- Older females are less likely to be alive
- Offspring will start reproducing earlier
Why do some organisms delay reproduction?
life-history trade-offs of early and late reproduction and the fitness costs to the parents associated with early reproduction
Why do we age/senescence?
Theory 1: mutation accumulation with age
Theory 2: Antagonistic pleiotropy
Both theories rest on the principle of selective advantage of early reproduction
What is the theory of mutation accumulation with age?
Selection will more effectively purge deleterious mutations affecting early-life traits than those affecting late-life traits. Therefore mutations affecting late-life traits accumulate
What is the theory of antagonistic pleitropy?
An allele that has a beneficial effect on one trait (e.g. early-life reproduction) has a detrimental effect on another trait (e.g. late-life reproduction)
What are life history trade-offs?
Give some examples.
The existence of both a fitness advantage and a concurrent fitness cost
Ex)
- survival/reproduction trade-offs
- early reproduction/late reproduction trade-offs
- offspring quality/quantity trade-offs
