Name __________________________________________ Period _________ Date ________________
Hardy Weinberg Equilibrium
How can a population’s genes change over time?
• All of the ______________________ of a population’s genes together make up a
____________________ ____________________
• Allele frequency - ____________________ of any specific allele in the gene pool
• Genetic equilibrium – a population in which the frequency of alleles
____________________ the ___________________ over generations
The Hardy-Weinberg Principle states:
• Genetic equilibrium will be reached if the frequency of alleles remains
________________________ generation after generation
• Genetic equilibrium = no _______________________________ occurring
Conditions necessary for genetic equilibrium are:
1. No _________________________ occurs
2. _____________________________ and _____________________________ do not occur
(population is isolated from other populations) - no gene flow
3. Population is very _______________________
4. Mating is totally __________________________
5. All individuals survive and reproduce ________________________
(no _______________________ selection)
Hardy-Weinberg Principle
• It is virtually ____________________________ to meet these conditions
• Allelic frequencies do _____________________ in populations, therefore
evolution occurs
• The main application of this principle is calculating ___________________ and
_________________________ frequencies in a population
In a population, the sum frequency of alleles will equal 1
• This can be expressed as:
• p+q=1
• Where:
• p = frequency of the _________________________ ____________________
• q = frequency of ___________________________ ______________________
Hardy-Weinberg Equation
2
2
p + 2pq + q = 1
• Where:
2
• p = frequency of individuals ________________________ __________________
• 2pq = frequency of ___________________________ individuals
• q
2=
frequency of individuals ________________________ ___________________
4 simple rules for calculating equations:
1. Find what q2 and q are first
• They can be determined with the information given to you in a
problem. The q2 population are the homozygous recessive
individuals. Once you solve for q2, take the square root to find q
2. Once you find what q is, you subtract that number from 1
• p + q = 1. That will give you p, or the number of dominant alleles
in a population
3. Square the p number to solve for p2
• This will give you the number of homozygous dominant
individuals in a population.
4. Now that we have p2, p, q2, and q, plug those numbers into the 2pq
• Check your work by plugging into each equation and see if they
equal 1
Practice Question
• If 98 out of 200 individuals in a population express the recessive
phenotype, what percent of the population are homozygous dominant?
(Recessive phenotype = homozygous genotype q2)
p+q=1
q2 =
98
200
q=
p=
p2 =
2pq =
= 0.49
p2 + 2pq + q2 = 1