Question

Please show all work step by step. Thank you.

1) The skin of the bright orange South American toad secretes a lethal neurotoxin. Assume that the toxin is produced by an enzyme encoded by a gene that has two alleles: T (dominant, wild-type enzyme/toxin) and t (recessive, no enzyme/toxin produced). The neurotoxin is secreted by means of a protein S produced by the wild-type gene S. The recessive allele s does not produce protein S (thus no secretion of the toxin can occur). A toad that cannot manufacture the enzyme/toxin and is heterozygous for the secretion gene is mated with a toad that cannot secrete the toxin and is heterozygous for the enzyme/toxin gene. What fraction of the progeny will be poisonous to the touch, that is, able both to manufacture and to secrete the toxin? Use probability to solve the problem.

2) The ability to taste the chemical phenylthiocarbamide is an autosomal dominant phenotype, and the inability to taste is recessive. If a taster woman with a nontaster father marries a taster man who in a previous marriage had a nontaster daughter.

What is the probability that their first child will be a nontaster girl?

What is the probability that they will have three children, two tasters and one non taster?

Answer 1

A) Ttss ?ttSs

progeny- TtSs TtSs ttSs ttSs

   Ttss Ttss ttss ttss

   TtSs TtSs ttSs ttSs

   Ttss Ttss ttss ttss

The fraction of progeny that will be poisonous to touch I.e. TtSs is 25%.

b) assume the gene for taster is T and for non taster is t.

mother. Father

   Tt tt

progeny -Tt. Tt Tt. tt

the probability of their first child to be non taster is 50%.

Te probabily of two nan taster children is 50% and one non taster is also 50%.