If two individuals are carriers of the cystic fibrosis allele, what is the probability that they would have a girl without cystic fibrosis? Show all your work (including the Punnett square) and express your answer as a value between 0 and 1 rounded to two decimal places. . (3 marks)
5 years ago
Answered By Micah Y
There are two parts to this question, assuming cystic fibrosis is not an X-linked trait.
Part 1: What's the probability that they would have a girl?
Draw a punnet square with the mother on one side (XX) and the father on the other (XY). The probability that the child is a girl is thus 0.5, because that's how many XX boxes are in the square.
Part 2: What's the probablilty that their child would have cystic fibrosis?
Both parents are carriers, which means they are heterozygous for a homozygous recessive trait. Drawing the punnet square, the probability that the child has cystic fibrosis is 0.25 (remember, we're looking for the homozygous recessive genotype).
Putting it all together: Multiplying the two probabilities gives us the probability that the child is both a girl and has cystic fibrosis - 0.5*0.25 = 0.125, rounded to two decimal places = 0.13.
5 years ago
Answered By Micah Y
There are two parts to this question, assuming cystic fibrosis is not an X-linked trait.
Part 1: What's the probability that they would have a girl?
Draw a punnet square with the mother on one side (XX) and the father on the other (XY). The probability that the child is a girl is thus 0.5, because that's how many XX boxes are in the square.
Part 2: What's the probablilty that their child would have cystic fibrosis?
Both parents are carriers, which means they are heterozygous for a homozygous recessive trait. Drawing the punnet square, the probability that the child has cystic fibrosis is 0.25 (remember, we're looking for the homozygous recessive genotype).
Putting it all together: Multiplying the two probabilities gives us the probability that the child is both a girl and has cystic fibrosis - 0.5*0.25 = 0.125, rounded to two decimal places = 0.13.
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