Exam Two Flashcards
Describe the two locus model (# of genes, gamete frequencies, possible combos)
Two genes, haplotype frequencies are gamete frequencies, ab/aB/Ab/AB
Give the general description of linkage equilibrium
The frequency of an allele is the same in both pairs (B pairs with A at the same rate (%) as it does with a)
What are the three definitions of linkage equilibrium?
The frequency of B in gametes carrying allele A is equal to the frequency of B in gametes carrying allele a
The frequency of any gamete haplotype can be calculated by multiplying the frequencies of the constituent alleles.
The quantity D, known as the coefficient of linkage disequilibrium, is equal to zero.
Give the general definition of linkage disequilibrium
The frequency of an allele is different in both pairs (B pairs with A at the different rate as it does with a)
Is linkage equilibrium/disequilibrium connected to allele frequencies?
No, there may be two groups of gametes with the same allele frequencies, but one is in linkage equilibrium and one is in linkage disequilibrium
What three things cause linkage disequilibrium in a population that was once in equilibrium?
Multilocus selection, drift, admixture
What is the general term for the mechanism that can restore linkage equilibrium in a population that is in disequilibrium, and what are the two subtypes?
Recombination
Independent assortment when genes are on different chromosomes and crossover between chromosomes when genes are on the same chromosome
Explain this equation: D= gABgab - gAbgaB
D is the coefficient of linkage disequilibrium, it is equal to zero during linkage equilibrium
Explain this equation: gAB’ = gAB -rD
It shows how much the gamete frequencies change from generation to generation. r is the recombination frequency and D is the coefficient of linkage disequilibrium.
Describe the maximum and minimum values of r, and what will increase or decrease it
r ranges from .5 when the genes are on different chromosomes to close to zero when the genes are very close together
Explain this equation: D’ = D(1-r)
This explains how much D changes from generation to generation. It will always be reduced (r is always above 0), but it is reduced faster with a higher value of r
Why was linkage disequilibrium distressing to evolutionary biologists, and why did they not have to worry?
It introduced another variable. They did not have to worry because it goes away quickly.
Describe Muller’s rachet
We all have some deleterious alleles, but in sexual reproduction, they are less likely to meet up.
In asexuals, the average number of deleterious mutations increases over generations
In a sexual population some progeny have fewer deleterious alleles the average, or more.The lower fitness are purged .
What are the three advantages of sexual reproduction?
Creation of new genotypes, eliminate genotypes with deleterious alleles, and recreates genotypes that were lost
What are quantitative traits?
Traits that are controlled by multiple genes
Describe the difference between genotypic variation and environmental varation
Genotypic is different genes, environmental is difference due to environment
Explain this equation: R=h^2S
R is response to selection (how much population will change), h superscript 2 is heritability in the narrow sense, and S is selection differential
What two things make up total phenotypic variation?
genetic variation and environment
What is the equation for heritability in the broad sense?
variation from different genes over total phenotypic varation
What three things make up genetic variability?
Interaction between genes, dominance effects, and additive effects (number of contributing alleles)
What is the equation for heritability in the narrow sense?
H superscript two is equal to variation from additive effects over total phenotypic variation
How is heritability in the narrow sense estimated?
Midparent value graphed against midoffspring value with the slope of the best fit line being equal to heritability
How do you calculate selection differential in nature?
Graph trait of parents against relative fitness, selection gradient is the slope, convert into S by multiplying by variance for trait
What is the equation for relative fitness?
Absolute fitness of a given phenotype over mean for population
What is the equation for absolute fitness?
number of offspring by a given phenotype over number produced by the most fit
Name the three types of selection for quantitative traits
Directional, Stabilizing, Disruptive
Describe directional selection and the effect on the population
Highest at one extreme, lowest on the other
Mean will move toward the favored extreme, more so when it is more heritable
Describe stabilizing selection and the effect on the population
Fitness is highest at intermediate values
Average remains the same, but distribution becomes narrower and variance is lower
Describe disruptive selection and the effect on the population
Fitness is highest at both ends
Average remains the same, distribution is flattened and variance is larger. After many generations, they may separate into two groups
Describe the set-up of the adaptive landscape
3D graph with X is frequency of one allele, Y is the frequency of one allele on another gene, and Z is mean fitness
What is the use of an adaptive landscape?
It shows where selection will take a population with a certain allele frequency
Of the five themes talked about in the last unit, which two will not jump local peaks in adaptive landscapes and which two will?
Selection (cannot go down) and Mutation (too small of a change)
Drift or Migration (they can determine the direction that selection will go, bigger change in allele frequencies)
Of the five themes talked about in the last unit, which will change the shape of the adaptive landscape?
Assortative mating, it changes the genotypic frequencies associated with allele frequencies
Define adaptation
A trait, or integrated suite of traits, that allows its possessor to succeed (survive and reproduce) in the fact of one or more agents of selection
What are the three cautions about assigning the word “adaption” to a trait?
Not every trait is an adaptation, differences are not always adaptive, and adaptations are not necessarily perfect
What are the three ways to determine if a trait is an adaptation (in order of reliability)?
Experiments, Observations, Comparative Evidence
Describe phenotypic plasticity
Phenotypic plasticity is an individual’s ability to change phenotype with changing environment
Describe evolutionary adaptation
Evolutionary adaptation is when traits of a population change due to environment
Give an example of trade-offs in adaptations
Hard for giraffe to drink with longer neck, easier to get mates
Describe the concept of genetic constraints to adaptation
The genetic raw material must be present for selection to act on it (the alleles have to already be in the population)
Describe pre-adaptation
A structure of trait that is in the right place in the right time for selection to give it a new function (create a new adaptation)
Describe selection pressures and trade-offs
Separate opposing selection pressures optimize rather than maximize trait values
What is S (selection differential) and how is it found?
S is a measure of the strength of selection used in quantitative genetics; equal to the difference between the mean phenotype of the selected individuals (for example, those that survive to reproduce) and the mean phenotype of the entire population.
What is R (selection response) and how is it found?
R is how much a population will change depending on the heritability and the selection differential. In quantitative genetics, the difference between the mean phenotype of the offspring of the selected individuals in a population and the mean phenotype of the offspring of all the individuals.
What are the three hypotheses in the Zonosemata fly experiment?
Nothing will happen, other spiders will be deterred, only jumping spider will be deterred
How can drift result in linkage disequilibrium?
No production of genotypes expected at low levels
Describe isogamy
gametes have the same size and morphology, no genders
Describe anisogamy and why it developed
gametes are different sizes, more mitochondria survive
Describe oogamy
one huge and non-motile gamete, one tiny and very motile
What are the consequences of oogamy?
Different parental investment
How do males/females maximize their number of offspring?
More mates and more resources
Define sexual dimorphisms
differences between the sexes in traits not involved in reproductive physiology
What are the three main ways males compete and what type of selection are they?
Fighting (sexual), Sperm (gametic or fecundity), Infanticide (gametic or fecundity)
Describe intrasexual competition
males fighting males
Describe intersexual competition
males fight to be chosen by females
What are the three main reasons females prefer traits that are harmful to zygotic fitness?
Genetic quality, runaway selection, acquisition of resources
When is there role reversal in parental investment?
When the males are the ones with more responsibility they choose the females who fight to be chosen
Do humans in polygamous tribes have the same gender restrictions on number of offspring?
Yes (males more mates, females more resources)
Do humans compete?
Kinda yes, mostly males are violent
Does violence translate to more progeny?
Maybe, maybe not (may depend on peer status in tribe)
Are males larger than females and do females prefer larger males?
Yes, and yes but this lessens with time (jury still out)
Do plants show asymmetry in parental investment (dioecious)?
Yes, they have oogamy. Parental function is sperm nucleus in pollen.
Maternal function is egg, embryo grows in ovule, food storage (endosperm and cotyledons), fruit (develops from surrounding ovary).
Do plants have the same limits on reproductive potential?
Yes, 50-50 yellow and white flower experiment
What are the two types of reproductive parts of flowers and what are the two non-reproductive parts?
Stamen-pollen
Carpel/Pistil-egg
Non-reproductive (parianth)
Petals Sepals
Describe the sexual dimorphisms in dioecious plants
Males also have to tend more flowers, and stronger odor, but equal quantity of nectar
Also have larger flower when pollinated by animals
