HardyWeinberg Equation Sometimes its fairly easy to determine

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 1. 2. 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 D+r=1 Ex. 75% of people have brown eyes while 25% have blue eyes 0. 75 + 0. 25 = 1

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

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

Sample problem 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 nontongue rolling gene? STEP 1: # of tt = 36% OR 0. 36 STEP 2: solve for number of t genes = t 2 = 0. 36 STEP 3: solve for number of T genes = T + 0. 6 = 1 T = 0. 4 STEP 4: solve for carriers = 2 T*t t = 0. 6 = 2(0. 4)(0. 6) = 0. 48 or 48% of pop. are carriers

PTC TASTER 4 in 25 students are non-tasters STEP 1: # of tt = 4/25 or 16% or 0. 16 STEP 2: solve for number of t genes = t 2 = 0. 16 STEP 3: solve for number of T genes = STEP 4: solve for carriers = 2 T*t T + 0. 4 = 1 = 2(0. 6)(0. 4) = 0. 48 or 48% of pop. are carriers t = 0. 4 T =0. 6

Cystic Fibrosis 1 in 2500 babies (Caucasians) STEP 1: # of cc = 1/2500 = 0. 04% or 0. 0004 STEP 2: solve for number of c genes = c 2 STEP 3: solve for number of C genes = STEP 4: solve for carriers = 2 C*c = 0. 0004 c = 0. 02 C + 0. 02 = 1 C = 0. 98 = 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 = 1/16, 000 or 0. 00625% or 0. 0000625 STEP 2: solve for number of c genes = c 2 STEP 3: solve for number of C genes = STEP 4: solve for carriers = 2 C*c = 0. 0000625 c = 0. 008 C + 0. 008 = 1 C = 0. 992 = 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 STEP 1: # of ss = 9% or 0. 09 STEP 2: solve for number of s genes = s 2 STEP 3: solve for number of S genes = STEP 4: solve for carriers = 2 S*s = 0. 09 S + 0. 3 = 1 = 2(0. 7)(0. 3) = 0. 42 or 42% of pop. are carriers (almost half) s = 0. 3 S = 0. 7

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 =