Cystic Fibrosis
Cystic fibrosis is an autosomal recessive disorder that affects 1 in 3 000 newborns with Caucasian background. It causes thick mucus build-up in various organs and can cause damages and problems in respiratory and digestive systems.
1. What is the frequency of the cystic fibrosis allele in the Caucasian population?
Show all your work and express your answer as a value between 0 and 1 rounded to three significant digits.
Let F and f be alleles for Cystic Fibrosis in which only having ff or both recessive alleles results in having cystic fibrosis.
1 newborn / 3000 newborns = 3.33...E-4% frequency of homozygous recessive genotype.
q^2 = 3.33...E-4
q = sqrt(3.33E-4)
= 0.0182574186% frequency for recessive allele.
= 0.0183%
2. What percentage of the Caucasian population would be carriers for cystic fibrosis?
Show all your work and express your answer rounded to two decimal places.
In genetics, the term carrier describes an organism that carries two different forms (alleles) of a recessive gene (alleles of a gene linked to a recessive trait) and is thus heterozygous for that the recessive gene.
p + q = 1
p + (0.0182574186) = 1
p = 1 - 0.0182574186
p = 0.9817425814% = frequency of dominant allele.
Total number of carriers would be 2pq
2(0.9817425814)(0.0182574186) = 0.0358481705% = 0.04% of the population would be carriers (heterozygous).
Therefore, 0.04% of the population would be carriers for cystic fibrosis.
3. 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. .
Two individuals are carriers of cystic fibrosis allele. Ff and Ff
F f
F FF Ff
f Ff ff
Probability that they would have a child without cystic fibrosis = 0.75
Probability that the child is a girl = 0.50
(0.50)(0.75) = 0.38% chance that the individuals will have a girl without cystic fibrosis.
I only need verification for question 2 and help with 3 (idk if I did it right), I put question one for reference but please let me know if I did it wrong. Sorry if this is too many questions, I figured it would be fine as technically they are all parts of one question.
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