The family tree shows the inheritance of a genetic characteristic - HSC - SSCE Biology - Question 11 - 2007 - Paper 1

To determine the probability of a daughter affected by the genetic characteristic, we must first analyze the genotypes of parents A and B based on their family tree.

1. Identify the Genotypes: Since the tree indicates the presence of affected individuals and normal individuals, we can infer the possible genotypes of parents A and B. If A has affected offspring from a normal parent, the inheritance is likely recessive.

2. Draw the Punnett Square: Assume A is a carrier (genotype Aa) and B is affected (genotype aa). The Punnett square would be:

   	a	a
   A	Aa	Aa
   a	aa	aa

3. Analyze the Results: This illustrates that:

   • There is a 50% chance for a daughter to be a carrier (Aa).
   • There is a 50% chance for a daughter to be affected (aa).

   Therefore, the probability that a daughter of parents A and B would be affected is 50%.

Final Answer: (C) 50%