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.

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 = ___________

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 0.75 + 0.25 = 1

Hardy-Weinberg If two hybrid parents are crossed: D r DD Dr rr DD Dr   D 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

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

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 + 0.6 = 1 T = 0.4 2T*t = 2(0.4)(0.6) = 0.48 or 48% of pop. are carriers

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 = 0.16 t = 0.4 T + 0.4 = 1 T = 0.6 2T*t = 2(0.6)(0.4) = 0.48 or 48% of pop. are carriers

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 0.0004 c2 = 0.0004 c = 0.02 C + 0.02 = 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)

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 0.00625% or 0.0000625 c2 = 0.0000625 c = 0.008 C + 0.008 = 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)

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 + 0.3 = 1 S = 0.7 2S*s = 2(0.7)(0.3) = 0.42 or 42% of pop. are carriers (almost half)

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 =