# What is an example hardy-weinberg equation practice problem?

##### 1 Answer

A question could look like:

**If #mathbf98# out of #mathbf200# individuals in a population express the recessive phenotype, what percent of the population would you predict would be heterozygotes?**

An explanation, walked through:

The Hardy-Weinberg equilibrium is a mathematical relationship of the alleles and genotypes in a population that meets certain characteristics. The relationships are as follow:

**Alleles:**

#p="frequency of the dominant allele"#

#q="frequency of the recessive allele"#

**Genotypes:**

#p^2="frequency of homozygous dominant genotype"#

#2pq="frequency of heterozygous genotype"#

#q^2="frequency of homozygous recessive genotype"#

From the question, we know that *recessive phenotype.* This means that these *homozygous recessive genotype*, the frequency of which is equal to

To determine what the actual frequency is, simply divide

However, we wish to find the frequency of the population that is *heterozygous*, which is equal to

**Finding #mathbfq#:**

#q^2=0.49#

Take the square root of both sides.

#q=0.7#

(This means that

Now that we've found the value of

**Finding #mathbfp#:**

Through the equation

#p+0.7=1#

Subtract

#q=0.3#

**Finding the frequency of heterozygotes:**

#"frequency of heterozygous genotypes"=2pq#

Substitute the known values for

#"frequency of heterozygous genotypes"=2(0.3)(0.7)=0.42#

Converting this into a percent, we see that