Question
In humans, the ability to taste(phenylthiocarbazide) PTC is inherited as a dominant gene (T orTaster). In a marriage between two heterozygous tasters (Tt):
a) What is the probability of 3 taster children?
b) What is the probability of 3 taster girls?
c) If they have 5 children, what is the probability that the first3 will be
tasters and the last 2 nontasters?
d) How many different ways could they have 3 taster and 2 nontasterchildren
in any order?
e) What is the probability that they will have 3 taster and 2nontaster children
in any order?
Explanation / Answer
make a square with the two parents genotypes on the top rowand on the left most column then find the combinations of the offspring. a.)Since the trait is dominant; the genotypes TT and Ttwill be tasters. Probability of one taster is 75% because there are 3/4 withthe TT or Tt genotype and the probability of 3 tasters is.75*.75*.75=.4287*100%=42.19% b.)The trait is a dominant gene, and the problem doesn't sayit's sex-linked, so the probability that there will be 3 tastergirls is the same, unless, you add in the probability that thechildren will be girls which is 50% so, the probability of having three girls is.50*.50*.50=.125*100%=12.5% if you multiply that with the probability of having threetasters .4219*.125*100%=5.27% Remember, this is not a sex-linkedtrait, so the probability of having three boys that are all tastersis the same!!! c.)If they have 5 children, chances that the first three willbe tasters is .753=.42187 the chances that they will have 2 non-tasters is.252=.0625 the chances that they will have them in that order is.0625*.42187=.02637*100%=2.64% .0264*3/5*2/5=.006336*100%=0.63% d.)Look up Permutations e.)the probability that they will have 3 taster and 2non-taster children in any order is: .753*.252=.0625*.42187=.02637*100%=2.64% the chances that they will have 2 non-tasters is.252=.0625 the chances that they will have them in that order is.0625*.42187=.02637*100%=2.64% .0264*3/5*2/5=.006336*100%=0.63% d.)Look up Permutations e.)the probability that they will have 3 taster and 2non-taster children in any order is: .753*.252=.0625*.42187=.02637*100%=2.64% T t T TT Tt t Tt tt