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Multiple Choice
If one parent is heterozygous (Aa) and the other is homozygous recessive (aa) for a dominant gene associated with Alzheimer's disease, what is the probability that their child will inherit the dominant gene?
A
25%
B
100%
C
75%
D
50%
Verified step by step guidance
1
Identify the genotypes of the parents: one parent is heterozygous (Aa) and the other is homozygous recessive (aa).
Set up a Punnett square to determine the possible genotypes of the offspring. The heterozygous parent (Aa) can contribute either 'A' or 'a', while the homozygous recessive parent (aa) can only contribute 'a'.
List the possible combinations of alleles from the parents: 'A' from the heterozygous parent with 'a' from the recessive parent (Aa), and 'a' from the heterozygous parent with 'a' from the recessive parent (aa).
Calculate the probability of each genotype in the offspring: there is a 50% chance of 'Aa' (dominant gene present) and a 50% chance of 'aa' (no dominant gene).
Since the dominant gene is represented by 'A', the probability that the child inherits the dominant gene is the probability of having the 'Aa' genotype, which is 50%.