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28 Cards in this Set

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Allelic frequency:
the proportions of diff alleles of a gene in a population
Genotype frequency:
proportion of homozygotes and heterozygotes in a population
What is p?
Frequency of allele A
What is q?
Frequency of allele a
What is 2pq?
Frequency of A/a
What is essential to remember about p and q?
p + q = 1
How do we find allele frequencies p and q?
By using the genotype frequencies.
What is the genotype frequency of p?
Freq AA + 1/2 freq A/a
What is the genotype frequency of q?
Freq aa + 1/2 freq A/a
What is the Hardy Weinberg Law?
Random mating results in an equilibrium distribution of genotypes which maintains constant genetic variation depending on allele frequencies of the gene.
What is the Hardy Weinberg law equation?
p^2 + 2pq + q^2 = 1
What does the equation allow?
Knowing Genotype frequencies (p^2 = A/A homozygous) allows you to figure out allele frequencies (p= fAA + .5Aa)
How do Hardy Weinberg calculations account for X-linked traits?
Females: just the same
Males: easier
-freq XA(Y) = p
-freq Xa(Y) = q
When does maximum heterozygosity occur?
When homozygosity is zero - b/c p'2 + 2pq + q'2 = 1
if 2pq (heterozygos) is 1, the other two must be 0.
What are 3 sources of variation?
1. Recombination
2. Mutation
3. Migration
What 2 processes result in recombination?
1. The normal reshuffling of whole parental chromosomes during meiosis (Homologous Chromosome segregation)
2. Crossing over at meiosis
Does mutation cause much variation?
Not alone - (A -> a) is quite slow
Why is mutation alone slow?
Because the frequency of normal A decreases in amount proportional to the mutation rate and to the amt of all genes still available to mutate.
How does mutation contribute to variation then?
Selection - based on ability to survive and reproduce
What is "fitness"?
The relative reproductive sucess
How do fitness and selection relate?
Reciprocally
When is fitness = 0? What would selection of the unmutated allele be in this case?
Fitness = 0 when no reproduction of the mutated gene.
Selection of UNmutated = 1
What are 2 diseases that exhibit fitness = 0?
-Why is fitness 0?
-Type of inheritance?
Tay-sach's; patients do not live to reproductive age. (auto rec)
Retinoblastoma: heterozygotes are lethal (auto dom)
What happens to fitness if reproduction is not 0, but it is diminished?
Fitness < 1
Why would fitness be <1 ?
-Physical problems
-Social
What happens if a mutation results in increased reproduction?
Fitness > 1
What is a disease that results in increased fitness?
Sickle cell - confers resistance to malaria in endemic populations
What type of SS phenotype resists malaria?
Trait - Ss