Exam 2 Flashcards
Evolution
Change in allele frequency in a population over time
Natural selection
unequal reproduction among individuals in a population based on phenotype
What are the five Hardy-Weinberg Assumptions?
No natural selection
No mutation
No migration
No mate preference
No genetic drift
With the Hardy-Weinburg model there is ______________ in allele frequency in a population over time.
NO change
What is the formula for Hardy-Weinburg?
p^2+2pq+q^2=1
When population is infinite and no evolutionary mechanisms at play, alleles combine _______________ (and in proportions to their frequencies) to form zygotes of next generation
randomly
Random mating is called
panmyxia
With pocket mice coloration was affected by the ________ locus
Mc1R
The two alleles of the coloration of dark mice were D and d. Dd=_______________ and dd=_______________
dark coats; light coats
Mismatch of light mice on dark substrate had survival of _______________
60-98%
In pocket mice, selection was against ____________ allele
d (light)
What is selection coefficient?
Quantification of strength of natural selection
The larger the selection coefficient the ________________ the action of natural selection
stronger
What was kuru?
a disease of the fore people of Papua New Guinea (epidemic in the late 1950s)
1976 _______________________became co-recipient of the Nobel Prize in Medicine for his “discoveries concerning new mechanisms for the origin and dissemination of infectious diseases.”
Carleton Gajdusek
What are the types of selection?
frequency independent and frequency dependent
Frequency independent selection is:
directional
overdominance (heterozygous advantage)
underdominance
Frequency dependent selection is:
positive and negative frequency dependence
Directional selection is where
one locus is favored over another
Overdominance:
Has a heterozygous advantage
Maintains allelic diversity in populations
Underdominance:
Selection against the heterozygote
Leads to fixation to one allele or the other depending on starting frequency
With frequency dependent selection the positive side-
More common allele is at fitness advantage
Fixation is inevitable
With frequency dependent selection the negative side-
Less common allele is at fitness advantage
Maintains allelic diversity in a population
Mutations are the ultimate source of ______________
variation
Mutations are __________ and there is no way for them to _______ future needs of organisms or occur when organisms “need” them
random; predict
Most mutations are neutral or at least slightly ____________
deleterious
Mutation as a ____________________ is very slow, but it can be significant given enough time
force of evolution
Favorable mutations can quickly become fixed in a population via ___________________
selection
Cell size _____________ over generations, large jumps indicate dramatic advantage of new mutations
increase
many mutations are deleterious, and we expect they well be eliminated by _________________
selection
if selection pressure is ______, and mutation rate is ______ for deleterious allele, we might find it in population at higher than expected frequencies.
low; high
If allele is recessive, this _________________________ (mutation selection balance) is expressed
equilibrium frequency
What is the equation for equilibrium frequency?
q=√(μ/s)
μ = mutation rate, s = selection coefficient (small: no effect to large: highly deleterious)
Spinal muscular atrophy results from loss-of-function alleles of the ________________
telSMN locus
Assortative mating: preferential mating between individuals with ____________ phenotypes
SIMILAR
Disassortative mating: preferential matings between individuals with ______________ phenotypes
DIFFERENT
Inbreeding is:
assortive
alleles are identical by descent
(F statistic)
Inbreeding depression causes
Reduction in fitness due to matings between genetic relatives
More risk of bringing deleterious recessive mutations together
Dissassortive mating involves
Mate with different phenotype
Increases heterozygotes
MHC preferences in humans involves
Large chromosomal region (over 200 genes)
Highly polymorphic
Involved in immune recognition
Migration is
Movement of alleles between population
Adults
Juveniles
Zygotes (seeds)
Gametes (pollen)
Migration homogenzies involves
With no opposing force (NS), migration tends to equalize allele frequencies
Example: Red bladder campion
What is genetic drift?
Only completely random mechanism of evolution
What does genetic drift result from?
random combination of alleles
Without infinite population sizes, ___________ may not combine in their expected mathematical probabilities
gametes
Genetic drift:
Deviations from expected frequencies due to chance effects in small populations
Genetic drift results in
Alleles fluctuate over time (without NS)
Alleles become fixed/lost
Frequency of heterozygotes decreases
Different populations experience different changes in allele frequency producing divergence
What are the two types of genetic drift?
Founder effect
Bottleneck
___________ populations experience more drift
Smaller
What is heterozygosity?
measure of variation in the population
What is OBSERVED heterozygosity?
fraction of individuals in a population who are heterozygotic at a particular loci
What is EXPECTED heterozygosity?
using allele frequencies from population, the fraction of heterozygotes predicted under H-W model
Wright-Fisher Model
predicts loss of heterozygosity by a factor of 1/2N with N as population size
Rate of loss is _____________ proportional to population size
inversely
What describes an effective population size?
Uneven sex ratio
Age structure
Fluctuations in pop size
Microsatellites
Act as selectively neutral, highly variable alleles
Selection strong and population large: ______________________more of a force
natural selection
Selection week and population small: _________________ is more of a force
genetic drift
Genetic drift __________ the probability of identity by descent over time
increases
phenotypic plasticity
Genotype different phenotypes in different environments (reaction norm)
What are some types of mutations?
Point mutations
Indels
Gene duplication
Inversions
Genome duplication
What type of mutations affect alleles?
point mutations
Indels–insertion deletions
What mutation affects genes?
gene duplication (polyploidy) (unequal crossing over, retroduplication (pseudogene)
What mutation affects chromosomes?
Inversions
Genome Duplication
What were the two hypotheses of the Luria Delbruck Experiment?
1.environment induced–equal distribution of resistance across cultures
2.spontaneous–unequal distribution
What did the Luria Delbruck experiment include?
Culture E. coli in a tubes with non selective media
Split into separate cultures and then grew on agar plates with a bacteriophage
