Calculate the exact probability that when parents who are both heterozygous for a
recessive disease have three children, the oldest will be affected, the middle one unaffected,
and the youngest affected.
The probability that all events would occur if found by multiplying the probabilities of the individual events.
.25*.75*.25 = ?
To calculate the exact probability of the given scenario, we need to understand the principles of Mendelian inheritance and use probability rules.
First, let's define the notation:
- P: Dominant allele (non-affected)
- p: Recessive allele (affected)
Given that both parents are heterozygous for the recessive disease, their genotypes can be represented as Pp.
Now, let's calculate the probability step by step:
1. Determine the probability of each child inheriting the alleles from the parents:
- For the oldest child: The probability of inheriting the recessive allele (p) is 1/2 from either parent since both parents are heterozygous (Pp).
- For the middle child: The probability of inheriting the dominant allele (P) is 1/2 from either parent since both parents are heterozygous (Pp).
- For the youngest child: The probability of inheriting the recessive allele (p) is 1/2 from either parent since both parents are heterozygous (Pp).
2. Multiply the probabilities together to get the overall probability:
To calculate the exact probability of the given scenario, we multiply the probabilities of each child inheriting the specific alleles:
Probability = (1/2) * (1/2) * (1/2) = 1/8
So, the exact probability that when parents who are both heterozygous for a recessive disease have three children, the oldest will be affected, the middle one unaffected, and the youngest affected is 1/8.
By following the principles of Mendelian inheritance and using probability calculations, we were able to determine the exact probability for the given scenario.