The correct answer is -
A) BbTt x bbTt
B) .5^4 or 1/16 or 0.0625
As it is given that Brachydactylus and PTC tasters both traits are autosomal dominant conditions which mean only one allele would be enough.
For Branchydactylus and For tasting : man and women will be heterogeneous.
The Genotype of man = BbTt
The Genotype of wife = bbTt
b. Answer = 0.0625
Bb X bb
b Bb( Brachydactylus) bb(normal)
b Bb (Brachydactylus) bb (normal)
The probability of a single child being Branchydactylus = 2/4 = 0.5
So, Probability of all 4 child being Branchydactylus = .5 x .5 x .5 x .5 = 0.0625