Exam One Flashcards
What is the definition of micro-evolution?
small changes in population allele frequencies
What is the definition of macro-evolution?
creation of new species
What is the definition of evolution?
a change in allele frequency in a population over time
What is the definition of population?
same gene, same location, same chromosomes, same geographical location
What is the definition of gene pool?
all of the gametes in a population
What is the definition of Hardy-Weinberg Equilibrium and what is the phrase used to describe it?
Given that p is the frequency of one allele and q is the frequency of the other and that p+q is one then genotypic frequencies will be p^2+2pq+q^2 which is one AND the allele frequencies will stay the same from generation to generation
Null hypothesis
What are the five requirements for Hardy-Weinberg Equilibrium to be true?
Mating is random, no migration, no mutation, infinite population size, no selection
What is the formula for getting genotypic frequency from allele frequency?
Population 1 has allele p with a frequency of X% and allele q with a frequency of X%
p^2 + 2pq +q^2 (AA is p^2, 2pq is Aa, and aa is q^2)
What is the formula for getting allele frequency from genotypic frequency? (on formula sheet)
Population 1 A1A1 has a frequency of X% and so to for A1A2 and A2A2
freq(homozygotes) + ½ freq(heterozygotes) is frequency of allele
What is the definition of selection?
differential lifetime reproductive success
What is the definition of fitness?
probability of survival and rate of reproduction relative to other phenotypes
What is the formula relating max fitness and actual fitness?
w=1-s
Describe zygotic selection
Zygote not surviving to adults
Describe sexual selection
male and female pairing
Describe fecundity selection
the production of sperm/egg (ex:low sperm count)
Describe gametic selection
sperm/egg forming zygotes (ex:low sperm quality)
Describe directional selection
allele frequencies move toward 1.0 or 0.0 (fixation or loss) in a asymptotic parabolic curve
Describe heterozygote advantage selection
allele frequencies stabilize between 1.0 and 0.0 (Equilibrium value is a function of s1 and s2)
Describe homozygote advantage selection
Allele frequency destabilized-
One allele will dominate the other (depends on current frequency and s’s)
Threshold of divergence (starting frequency needed to dominate) is a function of s1 and s2
How do you calculate mean fitness? (on formula sheet)
Mean fitness is equal to p^2(wAA) + 2pq(1wAa) + q^2(waa)
p^2 + 2pq +q^2 (AA is p^2, 2pq is Aa, and aa is q^2)
What is the definition of mutation?
change one allele into another allele (new or existing)
How do you find the new frequency of the alleles after some ps change to qs?
P has changed by -p*mutation rate
Q has changed by +p*mutation rate
What is the formula for the frequency of an allele after many generations of mutation? (formula sheet)
pn = po * e^-mutation rate times n
Pn is frequency after n generations
Po is frequency now
Mutation rate is rate that the allele mutates into another
What is the equilibrium value for mutation-selection balance? (on formula sheet)
How will it change if each component is larger or smaller?
Equilibrium value (q with a ^ above it) is equal to the square root of the mutation rate divided by s
If the mutation rate increases, the value will increase
If fitness increases (s is smaller), the value will increase
Describe the relative fitness required for directional selection
Highest fitness at one extreme and lowest at the other (can tie for lowest)
Describe the relative fitness required for heterozygote advantage selection and the phrase used to describe it
Heterozygotes have the maximum fitness (1), the others are lower
overdominance
Describe the relative fitness required for homozygote advantage selection and the phrase used to describe it
Heterozygotes have the lowest fitness
underdominance
What is the definition of an allele, where do they come from, and how many do adults and gametes have?
Different forms of a gene, each child receives one from each parent (adults have two, gametes have one)
What will happen to an allele that is lost or fixed?
It will stay that way, assuming no mutation or migration
Describe frequency dependent selection
the higher the frequency of an allele the higher the s value it is associated with (its fitness lowers in connection to how prevalent it is)
Define migration
gene flow from one population to another
What is the equation that is equal to the frequency of an allele after migration? (on formula sheet)
Pnew=m * pmigrant + (1-m) * pnative
M is % migrants
1-m is % natives
Pnew is new frequency
Pmigrant is frequency of allele among individuals that migrated
Pnative is frequency among native population
Compare migration and selection
Migration changes allele frequencies, but does not lead to adaptations (can affect direction of change)
What must happen after a migrant population meets the native population?
Admixture, or random mating
Define genetic drift
Random changes in allele frequency
How does the strength of genetic drift vary with size of population?
Smaller population is more drift
Are allele frequencies more likely to change or remain the same in a very small population?
Change
When is frequency of heterozygotes at a maximum?
When the allele frequencies are .5 and .5
Describe the relationship between population, effective population, and frequency of heterozygotes
Because the rate at which heterozygotes is lost (genetic drift) is a function of population size, population size can be estimated with loss of frequency of heterozygotes. However, the effective population size is almost always smaller than the actual population size (pop size will be estimated low) because
not all members of a population will reproduce.
Describe the Founder Effect
a small sample of a population forms a new population that only breeds among themselves and the resulting population has different allele frequencies than the original
(small differences in sample + genetic drift)
Describe assortative mating vs selection
Mating is not random - greater occurrence of like/like or unlike/unlike
Not selection - All genotypes still have the same rate of reproduction (all still mate and have same number of kids)
Describe positive assortative mating
like/like or inbreeding
Describe negative assortative mating
unlike/unlike or outbreeding
What is the most severe inbreeding?
Breeding with yourself
What sort of frequencies does assortative mating change?
Genotypic
What is the relationship between positive assortative mating and frequency of heterozygotes? (can be extrapolated to homo and outbreeding)
Positive assortative mating reduces heterozygotes
What is the definition of the coefficient of inbreeding? (F)
Probability of homozygote by descent (ancestor gave them a gene twice)
What is the equation for the coefficient of inbreeding in a population? (on formula sheet)
F= 1- (het0/2pq)
Het0 is observed frequency of heterozygotes
2pq represents expected frequency of heterozygotes (if random mating)
Describe the information learned if F is 0,<0,>0
=0 then it is in HWE
>0 then positive assortative mating or inbreeding
<0 then negative assortative mating or outbreeding
What are the four major patterns of selection?
Directional, heterozygote advantage, homozygote advantage, frequency dependent
What is the definition of inbreeding depression?
Lowering of mean fitness when there is directional selection and inbreeding
What are the three observations that were learned from experiments with the coefficient of inbreeding depression?
Inbreeding depression increases with age, increases with stress, and is variable between genotypes
Name the three mechanisms that nature uses to avoid inbreeding
Mate choice, reproductive systems, dispersal
Give two examples of mate choice (avoiding inbreeding)
Young females do not mature to breeding condition while father is dominant male, Plant self-incompatibility, mammalian MHC
Describe dioecy (plants)
Male and female plants
Describe monoecy (plants)
Male and female flowers on the same individual (but different place)
Describe heterostyly (plants)
Structure of the flower has male and female parts in the same flower, but the stigma and the style (female) are very tall, while the stamen (male) is very short so the pollen won’t fall on the female parts
Describe timing (plants)
Stamen and pistil will not mature at the same time
Give two examples of dispersal (avoiding inbreeding)
Mammals- Males disperse to new community
Birds- Females disperse to new community
Describe the situation in which inbreeding is beneficial
Homozygous Advantage
How common is cystic fibrosis? (one in #)
1/2500
What disease was used to detect a certain pattern of selection in DeltaF508?
Typhoid fever
What is the F value in barn mice? (experiment) (compare to 0)
<0, outbreeding
