Chapter 20: Population genetics, evolution at the population, species, and molecular levels Flashcards
What is the definition of a population?
group of organisms of the same species living in the same geographical area
What is the definition of the gene pool?
all alleles of all the genes present in a population
Describe genotypic frequency
proportion of individuals in a population with a specific genotype
describe allelic frequency
proportion of a particular allele in a population
What does hardy-weinburg principle allow us to ask
What affects the frequencies of alleles in a population
Describe the peppered moth phenomenon
wild type moths can blend into the lichened tree trunk?????????
Describe the conditions that will determine if allelic frequencies will remain constant?
- population is so large that allelic variations do not occur by chance
- mating is random
-all genotypes have equivalent fertility and viability
———natural selection does not occur
-mutation does not occur
-migration into or out of the population is absent
-genetic drift is absent
Describe the allelic equation
p + q = 1
P= frequency (f) of alleles = 1
p = (f) of 1st allele (dom)
q = (f) of 2nd allele (rec)
(homo/hetero doesnt matter)
Describe the genotypic equation
p2 + 2pq + q2 = 1
p2 = pp = frequency of 1st homozygous genotype (dom)
2pq = frequency of heterozygous genotype
q2 = qq = frequency of 2nd homozygous genotype (rec)
Describe how to solve a codominance problem?
MM, MN, NN, total = 100
Q = frequency of each allele
frequency of M allele = (MM x 2) + (MN) / 200
frequency of N allele = (NN x 2) + (MN) / 200
describe how to solve a dominance problem?
Q = frequency of hetero and homozygous dominant genotypes?
% of species resulting from homozygous recessive allele
1: q^2 = (% in decimal form)
2: q = sqrt(q^2)
3: p = 1 - q
4: 2pq = heterozygous
5: p^2
6: p = sqrt(p^2) = homozygous
describe how to solve an X- linkage problem?
Q = what is the expected frequency of carrier (heterozygous) females
1: q = fraction of affected (ex: 1/50)
2: p = 1 - q
3: 2pq = carrier (hetero)
Q= frequency of affected (homozygous) females?
1: q^2 = affected (homo)
What are some factors that affect allele and genotypic frequencies?
- mutations
- genetic drift
—-chance factors… changes in allele frequencies
—-smaller populations
What is the founder effect?
an example of genetic drift… small portion of population is separated
ex: church of the brethren
Describe the bottleneck effect?
genetic drift… a portion of the population is gone
Describe the case of the cheetahs?
Example of bottleneck effect, the cheetahs mating within groups that were cut off from the rest of the population
- were mating with close relatives… developed inbreeding depression
Describe the case of the hapsburg jaw?
Another example of bottle necking…
