Final answer:
The proportion of offspring expected to be AaB_cc in a cross between AaBbCc and AaBbcc is calculated using the probabilities for each gene pair and the product rule. The result is a 3/16 chance of an offspring being AaB_cc, making the correct answer, option 3).
Step-by-step explanation:
In a cross between an individual with genotype AaBbCc and another with genotype AaBbcc, we want to calculate the proportion of offspring expected to be AaB_cc (where '_cc' symbolizes either Cc or cc). We will use the probability method involving the Punnett square or forked-line method to solve this problem.
Firstly, we need to consider each gene pair separately:
For gene A, the cross is Aa x Aa. This yields a probability of 1/2 for offspring to be Aa (heterozygous).
For gene B, the cross is Bb x Bb. The possibility of an offspring being B_ (either Bb or BB) is 3/4, which includes both the heterozygous (Bb) and the homozygous dominant (BB) possibilities.
For gene C, since one parent is Cc and the other is cc, there's a 1/2 probability of an offspring being _cc (either Cc or cc).
Using the product rule of probability, we multiply these individual probabilities because each event is independent:
The combined probability for an offspring to be AaB_cc is (1/2) × (3/4) × (1/2) = 3/16.
The correct answer from the choices given is therefore 3/16, which corresponds to option 3).