A) 36%B) 60%C) 40%D) 16% and 48%E) 64% (dominant) and 36% (recessive)
The Hardy-Weinberg Principle
Think. Pair. Share.Solve for p or q in each of the following:108 – q = 80 q=? q = 28p + 30 = 65 p=? p = 3552 - 420 + q2 = 5 q=? q = 20
The Hardy-Weinberg PrincipleGodfrey Hardy and Wilhelm Weinberg developed amathematical equation to predict allele frequencies inpopulations: The Hardy-Weinberg Principle. Played cricket with his Independently developed the friend Reginald Punnett. principal at the same time.
The Hardy-Weinberg PrincipleThe Hardy-Weinberg Principle is used to predict alleledistribution and frequencies within a population. Not always accurate.
Think. Pair. Share.Recall what the following genetics terms mean:GenotypePhenotypeAlleleRecessiveDominantHomozygousHeterozygous
The Hardy-Weinberg PrincipleSuppose a population has only 2 eye colour alleles:Brown (B)(dominant) and blue (b)(recessive). BB Bb bb bb bb
The Hardy-Weinberg Principle p+q=1Where:p is the percentage of dominant alleles in the populationq is the percentage of recessive alleles in the population
The Hardy-Weinberg PrinciplePercentage of alleles means that 2 alleles were countedfor each person, then added up: BB Bb bb bb bb
The Hardy-Weinberg Principle Alleles present: 3 brown alleles (B) 7 blue alleles (b) Thus: p = 3 / (3 + 7) = 0.30 = 30% q = 7 / (3 + 7) = 0.70 = 70%
The Hardy-Weinberg Principlep = 30% means 30% of the alleles in the population are Bq = 70% means 70% of the alleles in the population are b Check: p+q=1
The Hardy-Weinberg Principle Now we know p+q=1 What if we do (p + q)2 = 12 ?
Hardy-Weinberg Equilibrium p2 + 2pq + q 2 =1Where:p2 is the percentage of homozygous dominant organismsEx. (BB) – person has brown eyes
Hardy-Weinberg Equilibrium p2 + 2pq + q 2 =1Where:2pq is the percentage of heterozygous organismsEx. (Bb) – person has brown eyes
Hardy-Weinberg Equilibrium p2 + 2pq + q 2 =1Where:q2 is the percentage of homozygous recessive organismsEx. (bb) – person has blue eyes
Think. Pair. Share.Do the math. Is this population in a Hardy-Weinbergequilibrium (does the population match p2 + 2pq + q2 = 1)? BB Bb bb bb bb
Hardy-Weinberg EquilibriumAllele distribution in a population can only be predicted ifit is not changing (or evolving).
Hardy-Weinberg EquilibriumThe Hardy-Weinberg Principle is only accurate if:1) no mutations occur.2) no selection occurs.3) there is no immigration or emigration.4) the population is large enough to avoid genetic drift.5) there is no horizontal gene transfer (bacteria).6) all mating is random.
Hardy-Weinberg EquilibriumPractice:1) You have sampled a population in which you knowthat the percentage of the homozygous recessive ("aa")genotype is 36%. Find the following: A) The frequency of the "aa" genotype B) The frequency of the "a" allele C) The frequency of the "A" allele D) The frequencies of the genotypes "AA" and "Aa" E) The frequencies of the two possible phenotypes if "A" is completely dominant over "a"