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The ability to taste the chemical phenylthiocarbamide is an autosomal dominat 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 taster girl?
A) 1/8 B) 3/8 C) 1/4 D) 1/2 E) 3/4

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Answer:

Option B is correct

Explanation:

Given -

"Ability to taste the chemical phenylthiocarbamide" is autosomal dominant while its inability is recessive.

Autosomal dominant means that even if one l

Let the allele for dominant trait i.e  "Ability to taste the chemical phenylthiocarbamide" be represented by "T"

and the allele for recessive trait i.e "Inability to taste the chemical phenylthiocarbamide" be represented by "t"

Genotype of a taster woman with a nontaster father is Tt

Genotype of  a taster man who in a previous marriage had a nontaster daughter is also Tt

Tt * Tt

TT, Tt, Tt, tt

Therefore probability of being a taster is [tex]\frac{3}{4}[/tex], and  the probability of being a nontaster is [tex]\frac{1}{4}[/tex]

Probability that their first child will be a taster girl is  equal to

Probability of being a taster [tex]*[/tex] Probability of being a girl

[tex]\frac{3}{4} * \frac{1}{2} \\=\frac{3}{8}[/tex]

Thus, option B is correct

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