Download The Hardy Weinberg principle allows us to see if microevolution is

POPULATION GENETICS AND THE HARDY-WEINBERG PRINCIPLE
The Hardy Weinberg principle allows us to see if microevolution is occurring in a
population for a particular trait. In order for equilibrium to occur (no change in the
frequency of the alleles….no microevolution) certain conditions must be met: 1. The
population must be large 2. No mutations 3. No migration in or out of the
population 4. Mating must be random
In the Hardy Weinberg theorem, p +q = 1. P represents the dominant allele and q
represents the recessive allele for a particular characteristic. The number one
represents all of the population that you are studying. If the dominant allele occurs
40% of the time (or .4), then the recessive allele occurs 60% of the time (or .6)
because .4 +.6 = 1
To determine allele frequency, the equation p2 + 2pq = q2 = 1 is used.
In this equation, p2 stands for the homozygous dominant genotype, 2pq for the
heterozygous genotype, and q2 for the homozygous recessive genotype. For the
recessive phenotype, if you know the phenotype, you know the genotype. If someone
has a recessive trait, then you can use the frequency of the recessive allele to plug into
this equation and figure out the rest!
For example, in a population of 1000, you notice that 49% of the population does not
have the ability to roll their tongue (rr). That means that q2 = .49. The square root of
.49 is .7, so q = .7. If q = .7, then p = .3. (remember that p+q =1). Now, plug in the
.3 and the .7 in the p2 + 2pq + q2 = 1 equation, and remember that there are 1000 in
the population and you can figure out the answer.
Here is the frequency of the alleles for tongue rolling in this population:
49% of 1000 = 490 rr
9% (.3 x .3) of 1000= 90 RR
42% of 1000 = 420 Rr