Question

2. The ability to taste the chemical PTC is determined by a single gene in humans with the ability to taste given by the dominant allele T and inability to taste by the recessive allele t. Suppose two heterozygous tasters (Tt) have a large family.
a. Predict the proportion of their children who will be tasters and nontasters. Use a Punnett square to illustrate how you make these predictions.b. What is the likelihood that their first child will be a taster? What is the likelihood that their fourth child will be a taster?c. What is the likelihood that the first three children of this couple will be nontasters?

Answer 1

Answer a)

        T       t

T     TT      Tt

t      Tt      tt

75% of the children will have the probability of being tasters. 25% will have the probability of being non- tasters.

Answer b)

There will be a 75% chance that their first child or their fourth child will be a taster.

The chances for every child will be the same because alleles assort independently during the time of gamete formation. Hence, the probability remains the same every time.

Answer c)

There will be a 25% chance for the first three offsprings to be non-tasters. 75% chances will be of them being tasters.

This is because the alleles assort independently each time during gamete formation. Hence, the chances will be the same every time.