Question

Suppose that a dominant allele (P) codes for a polka-dot tail and a recessive allele (p) codes for a solid colored tail. If two heterozygous individuals with polka-dot tails mate, what's the probability of the phenotype and genotype combinations of the offspring? A. 75 percent chance of a polka-dot tail and 25 percent chance of a solid colored tail (75 percent Pp; 25 percent pp) B. 75 percent chance of a polka-dot tail and 25 percent chance of a solid colored tail (25 percent PP; 50 percent Pp; 25 percent pp) C. 25 percent chance of a polka-dot tail and 75 percent chance of a solid colored tail (25 percent PP; 50 percent Pp; 25 percent pp) D. 50 percent chance of a polka-dot tail and 50 percent chance of a solid colored tail (50 percent PP; 50 percent pp)

Answer 1

Before we answer your question, let's put your data into a Punnet square. The problem says that two heterozygous individuals will mate, so that means their phenotype is Pp. 

         P       p
P     PP     Pp

p      Pp     pp

When you read a Punnet square to look for gentoypic ration, it refers to the Genotype, or let's just say the code and just count how many genotypes combinations you see out of the total, which in this case is 4. 

PP = 1 out of 4 = 25%
Pp = 2 out of 4  = 50%
pp = 1 out of 4  = 50%

When we look at phenotype, we look for the trait that is expressed. If that is the case, you should remember that the dominant trait is ALWAYS expressed over the recessive. So if the genotype is Pp, the trait of the P is going to be expressed. 

Polka-dot (P) = PP and Pp = 3 out of 4 = 75% 
Solid (p) pp = 1 out of 4 = 25%
 
So looking at the result, the answer would then be B. 75% chance of a polka-dot tail and 25% chance of a solid tail (25%PP, 50%Pp and 25%pp).