1. A Better Explanation of the Hardy Weinberg Equation
Population Genetics
A Better Explanation of the Hardy Weinberg Equation

2. P2
Genotype = the 2 alleles that an individual has for a particular trait.
Genotype represented by p2 = homozygous dominant
Represents the percentage of individuals that have the homozygous dominant genotype.
Example: GG, where G = the dominant allele for a trait.
If p2 = .25, then it would mean that 25% of the population has this genotype.

3. 2pq Genotype represented by 2pq = heterozygous
Represents the percentage of individuals that have the heterozygous genotype.
example: Gg, where G = a dominant allele for a traitand g = a recessive allele for a trait.
If 2pq = 50% it would mean that 50% of the individuals in a population would have the heterozygous genotype.

4. q2 Genotype represented by q2 = homozygous recessive.
Represents the percentage of individuals in the population that have the homozygous recessive genotype.
Example: gg, where g = the recessive allele for a trait.
If q2 = .25, then it would mean that 25% of the population has the recessive genotype for a trait.

5. p Allele = a version of a gene.
Allele represented by p = dominant allele
Represents the percentage of dominant alleles out of all of the alleles present in a population for a trait. = allele frequency
Example: If p = .55, then it would mean that 55% of the alleles in a population were G alleles.

6. q p + q = 1 Allele represented by q = recessive allele
Represents the % of recessive alleles out of all of the alleles in a population for a trait.
Example: If q = .45, then it would mean that 45% of the alleles in a population were the g allele.
p + q = 1
Means that the % of dominant alleles plus the % of recessive alleles = all of the alleles for a trait in a population.

7. p2 + 2pq + q2 = 1
Refers to the % of genotypes of individuals in a population.
Means the % of homozygous dominant individuals plus the % of heterozygous individuals plus the % of homozygous recessive individuals = all of the possible genotypes of the individuals of the entire population for a trait.

8. Example
A population of 200 painted turtles became stranded on a different island. Painted turtles can have long or short necks.
Having the dominant allele (L) results in having a long neck for painted turtles. Of the 400 alleles for the neck length gene, 120 of them are dominant (L). The rest of the alleles are recessive. Calculate the allele frequency for the dominant allele (p) and the recessive allele (q) for this population. Use this information to predict how many of the 200 painted turtles are LL, Ll, and ll.

9. Questions to Ask Yourself
What is the size of the population?
How many alleles are there in the population?
What information should I use first?
Do the answers make sense?