Cycle 6 part 2 Flashcards
Heterozygote advantage and heterozygote disadvantage have two differences:
-Different effects on genetic variation
-Different importance of starting allele frequencies
Heterozygote advantage and heterozygote disadvantage have in common:
both can only occur if heterozygotes have a different phenotype than either homozygote
Heterozygote advantage and heterozygote disadvantage are not possible if one allele is completely _______ and the other is completely ________
Dominant and recessive
Rare alleles are mostly in heterozygotes or homozygotes
heterozygotes
Common alleles are mostly in heterozygotes or homozygotes
homozygotes
Het advantage: rare alleles increase or decrease?
increase
Het disadvantage: rare alleles increase or decrease
decrease
A genotype’s ____________, W, is a measurable quantity (average lifespan, number of eggs, number of grandoffspring)
absolute fitness
A genotype’s ________, w, is its absolute fitness divided by the absolute fitness of the most successful genotype
relative fitness
If WAA = WAa=Waa what type of selection is occurring
No selection
Genetic drift: random sampling error
Most powerful in ____ populations, but happens whenever population size is ____
small, finite
Iclicker question: If WAA = 20, WAa = 15, and Waa = 12, what is the relative fitness of genotype aa? That is what is waa?
0.6
Which situation describes heterozygote disadvantage?
WAA>WAa<Waa
If wAA = wAa > waa what tu[e pf selection is occuring?
Selection against allele a
T/F Genetic drift is restricted to bottlenecks and founder events…
FALSE: it is always happening
If f(A) decreases and f(a) increases due to genetic drift in one generation, what will probably happen in the next generation?
f(A) and f(a) will probably change again, but we can’t predict which will decrease and which will increase
CAN PREDICT: Over many generations, drift tends to _____ genetic variation
remove
Usually, but not always, the ___ allele gets removed
rarer
If mating is not random with respect to genotype: Like with Like at one trait is ______
Assortative mating
Opposites attract at one trait:
disassortative mating
Like with like genome-wide?
Inbreeding
Opposites attract genome-wide?
Inbreeding avoidance
Assoritve mating perturbs ____ but doesn’t cause ______
HWE, evolution (out of HWE but still not evolving because allele frequencies are not changing)
Does inbreeding cause evolution?
NO
If not, why are genetic disorders so common within highly inbred populations or inbred royal dynasties?
Most genetic disorders are associated with recessive alleles. So even though inbreeding doesn’t change the frequencies of the allele, it increases the proportion of homozygous recessive genotypes
Homozygous ______ genotypes that are likely to express harmful alleles
recessive
Iclicker questions: How can we determine whether a population is in HWE at a particular locus?
Calculate allele frequencies, and check whether these match the observes genotype frequencies
In a pond of 100 fish: 16 are black (BB), 48 are gray (Bb), 36 are white (bb). What can you reasonably conclude about selection at this locus?
Selection is not occuirng
In a flock of 100 birds, 5 have red feathers (RR), 90 have purple feathers (Rr) and 5 have blue feathers (rr), which of these explanations is most likely?
A) Because p = q, the population is in HWE at this locus. Therefore, selection is not operating on feather color
B) The population is either inbred or mating assortatively (like with like) at those locus
C) Heterozygote advantage at this locus
B
