A healthy twenty-seven-year-old female presents to the physician for genetic counseling with her husband. They would like to become pregnant in the near future, but they have concerns that their offspring may develop cystic fibrosis. The wife’s sister has cystic fibrosis, an autosomal recessive disorder with an incidence of approximately 1 in 90,000. The husband’s history is noncontributory. What is the probability of the husband being a carrier?
Question
A healthy twenty-seven-year-old female presents to the physician for genetic counseling with her husband. They would like to become pregnant in the near future, but they have concerns that their offspring may develop cystic fibrosis. The wife’s sister has cystic fibrosis, an autosomal recessive disorder with an incidence of approximately 1 in 90,000. The husband’s history is noncontributory. What is the probability of the husband being a carrier?
Solution
The probability of the husband being a carrier for cystic fibrosis can be calculated using the Hardy-Weinberg equation, which is used to estimate the frequency of alleles in a population.
The equation is p^2 + 2pq + q^2 = 1, where:
- p^2 represents the frequency of the homozygous dominant genotype (normal)
- 2pq represents the frequency of the heterozygous genotype (carrier)
- q^2 represents the frequency of the homozygous recessive genotype (affected)
Given that the incidence of cystic fibrosis is 1 in 90,000, we can use this to calculate q^2.
q^2 = 1/90,000 = 0.000011
To find q (the frequency of the recessive allele in the population), we take the square root of q^2.
q = √0.000011 = 0.0033
The frequency of the dominant allele (p) can be found by subtracting q from 1, as p + q = 1.
p = 1 - q = 1 - 0.0033 = 0.9967
Finally, we can find the frequency of carriers (2pq) in the population.
2pq = 2 * 0.9967 * 0.0033 = 0.0066
So, the probability of the husband being a carrier is approximately 0.0066, or 0.66%.
Similar Questions
A healthy twenty-seven-year-old female presents to the physician for genetic counseling with her husband. They would like to become pregnant in the near future, but they have concerns that their offspring may develop cystic fibrosis. The wife’s sister has cystic fibrosis, an autosomal recessive disorder with an incidence of approximately 1 in 90,000. The husband’s history is noncontributory.
If both the mother and the father are carriers for the cystic fibrosis gene, what are the chances that their child will be a cystic fibrosis carrier?
If a couple that are both heterozygous carriers of the cystic fibrosis allele have children, the chance that both their first and their second child are carriers is 0.5 x 0.5, or 25%, as determined by theMultiple choice question.
If a healthy young couple are both carriers of cystic fibrosis, the chance that their future child will have this serious illness isMultiple Choice0%.25%.75%.50%.100%.
3. If Sophie conceives a child, and the father neither has cystic fibrosis nor is a carrier, what are the chances that the child would have cystic fibrosis?a. 0%, because the child must receive the bad gene from both parentsb. 50%, because there is a 50% chance that Sophie will pass along the bad genec. 100%, because Sophie has the conditiond. 75%, because Sophie has the condition but the father does note. 25%, because only one in four gametes will carry the bad gene
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