1. Hardy-Weinberg Equation
Sometimes, it’s fairly easy to determine if you have a genetic disorder – the symptoms can be very obvious. However, just because you don’t have a particular genetic disorder doesn’t mean you don’t carry it. People go to genetics counselors who collect information about your family history and build a pedigree. From these pedigrees and using a mathematical equation, they can determine the chance that you are a carrier.

2. Hardy-Weinberg Equation
Definition – An equation used to figure out how common the carriers are based on knowing how often a trait is inherited.
Frequency – How often something occurs;
usually written as a decimal. 25
Ex. 1 out of 4 people have blue eyes = ______%
0.25
As a decimal = ___________

3. Hardy-Weinberg Equation
D = dominant r = recessive
All the genes present in a population of people:
frequency of dominant genes + frequency of recessive genes = 100% OR
Ex. 75% of people have brown eyes while 25% have blue eyes
D + r = 1
= 1

4. Hardy-Weinberg If two hybrid parents are crossed: D r DD Dr rr DD DrD r DD Dr rr
frequency of purebred Dom. ind. = D2
frequency of hybrid ind.= D*r +D*r OR 2D*r DD Dr
frequency of purebred rec. ind.= r2 Dr rr D2
+ 2Dr
+ r2
= 1
CARRIERS
HAVE RECESSIVE TRAIT

5. Hardy-Weinberg If two hybrid parents are crossed: D r DD Dr rrD r DD Dr rr
D2 + 2Dr + r2 = 1
Hardy-Weinberg equations: 1.
D + r = 1 2.
Have recessive trait = r2 3.
Carriers = 2Dr

6. Sample problem 36% OR 0.36 t2 = 0.36 t = 0.6 T + 0.6 = 1 T = 0.4
If tongue rolling (T) is dominant to non-tongue rolling (t), and 36% of the population are non-rollers how common are the carriers of the non-tongue rolling gene?
STEP 1: # of tt =
STEP 2: solve for number of t genes =
STEP 3: solve for number of T genes =
STEP 4: solve for carriers =
36% OR 0.36
t2 = 0.36 t =
0.6
T = 1 T =
0.4
2T*t = 2(0.4)(0.6) =
0.48 or 48% of pop. are carriers

7. PTC Taster 4 in 25 students are non-tasters 4/25 or 16% or 0.16
STEP 1: # of tt =
STEP 2:solve for number of t genes =
STEP 3: solve for number of T genes =
STEP 4: solve for carriers =
4/25 or 16% or 0.16
t2 = t =
0.4
T = 1 T =
0.6
2T*t = 2(0.6)(0.4) =
0.48 or 48% of pop. are carriers

8. Cystic Fibrosis 1 in 2500 babies (Caucasians) 1/2500 = 0.04% or 0.0004
STEP 1: # of cc =
STEP 2:solve for number of c genes =
STEP 3: solve for number of C genes =
STEP 4: solve for carriers =
1/2500 = 0.04% or
c2 = c =
0.02
C = 1 C =
0.98
2C*c = 2(0.98)(0.02) =
0.039 or 3.9% of pop. are carriers
(approx. 1 in every 25 people)

9. Cystic Fibrosis 1 in 16,000 babies (African-American)
STEP 1: # of cc =
STEP 2:solve for number of c genes =
STEP 3: solve for number of C genes =
STEP 4: solve for carriers =
1/16,000 or % or
c2 = c =
0.008
C = 1 C =
0.992
2C*c = 2(0.992)(0.008) =
0.015 or 1.5% of pop. are carriers
(approx. 1-2 in every 100 people)

10. Sickle Cell Anemia 9% of population in Africa 9% or 0.09 s2 = 0.09 s =
STEP 1: # of ss =
STEP 2:solve for number of s genes =
STEP 3: solve for number of S genes =
STEP 4: solve for carriers =
9% or 0.09
s2 = 0.09 s =
0.3
S = 1 S =
0.7
2S*s = 2(0.7)(0.3) =
0.42 or 42% of pop. are carriers
(almost half)

11. Genetic Disorder Project
Assignment #4
Use the Hardy Weinberg equation to determine the frequency of carriers for your assigned genetic disorder.
STEP 1: # of ss =
STEP 2:solve for number of s genes =
STEP 3: solve for number of S genes =
STEP 4: solve for carriers =