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Population Genetics
HardyWeinberg Equations
Let us start with a given trait that has two alleles T and t. To find the frequency of allele T(p) in
the population, we would use the following formula:
p = (# of copies of T in the population) / (total # of copies of all alleles in the population); or p =
(2(# of individuals homozygous for T) + (# of individuals heterozygous for T)) / 2(# of
individuals in the population). We can find the frequency of allele t (q) in the same way.
Once we have the values of p and q, we can set up an equation based on the HardyWeinberg
equilibrium. If the frequency of each allele is constant, then the following equation, called a
HardyWeinberg Equation, is always true:
(
p
+
q
)
2
= 1 ; or
p
2
+2
pq
+
q
2
= 1
The second form of the above equation is the most useful, since each of its factors represents a
portion of the population.
P
2
and
q
2
represent those individuals homozygous for T and t,
respectively, while 2pq represents all heterozygous individuals. Using these equations, we can
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This note was uploaded on 01/27/2012 for the course BIOLOGY BSC1005 taught by Professor Rodriguez during the Winter '09 term at Broward College.
 Winter '09
 Rodriguez
 Biology, Genetics, Population Genetics

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