Question

Sam detests the taste of broccoli, coffee, chocolate, and other bitter foods. He is homozygous dominant for PTC (P) and heterozygous for thiourea (T). Mary, alternatively is not adverse to any of those foods and is heterozygous for PTC and homozygous recessive for thiourea.

a. What will be the genotypic and phenotypic frequencies of their offspring?

b. Is it possible for any of their potential children to not be able to taste PTC?

Answer 1

Answer-

According to the given question-

Sam cannot taste the taste of coffee broccoli, , chocolate, and other bitter foods and is homozygous dominant for Phenylthiocarbamide or PTC which means have genotype PP, and heterozygous for thiourea which means have genotype for thiourea Tt. while Mary, is heterozygous for PTC which means have genotype Pp and homozygous recessive for thiourea which means have genotype tt.

When we make a cross between sam and mary we get-

PPTt Pptt

	Pt	Pt	pt	pt
PT	PPTt (PTC , Thoiurea tester )	PPTt (PTC , Thoiurea tester )	PpTt (PTC , Thoiurea tester )	PpTt (PTC , Thoiurea tester )
Pt	PPtt (PTC tester, thiourea nontester)	PPtt (PTC tester, thiourea nontester)	Pptt (PTC tester, thiourea nontester)	Pptt (PTC tester, thiourea nontester)
PT	PPTt (PTC , Thoiurea tester )	PPTt (PTC , Thoiurea tester )	PpTt (PTC , Thoiurea tester )	PpTt (PTC , Thoiurea tester )
Pt	PPtt (PTC tester, thiourea nontester)	PPtt (PTC tester, thiourea nontester)	Pptt (PTC tester, thiourea nontester)	Pptt (PTC tester, thiourea nontester)

here half of their offspring are PTC as well as Thiourea tester and half are PTC tester but thiourea nontester i.e. 50 % each.

Genotype - PTC tester, Thoiurea tester = PPTt and PpTt

PTC tester, Thoiurea non-tester =PPtt and Pptt .

Phenotype = PTC tester, Thoiurea tester : PTC tester, Thoiurea non-tester = 1 : 1.

All their offspring are PTC tester but some are thiourea nontesters.