Answers pedigree problems

Answers pedigree problems - carriers A Sex linked...

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Answers to Genetics Questions-3 (Pedigrees) 1. The probability that A is a cystic fibrosis carrier is 2/3 and that B is a carrier is also 2/3 so, the probability of any child being born with cystic fibrosis is given by: 2/3 x 2/3 x 1/4 = 4/36 = 1/9 2. I-1 R/r I-2 R/Y II-1 R/Y II-2 r/Y II-3 R/r II-4 R/Y III-1 r/Y 3. The probability that the next son born will have the gene for Atkinson’s disease is 1/2, but since the trait is only 60% penetrant, the probability, the probability he will actually have the disease is 1/2 x 60/100 = 0.30 4. If a trait is rare, assume that people marrying into the family are not
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Unformatted text preview: carriers A. Sex linked Recessive (it only appears in males) B. Sex linked Dominant (note that no affected male has an affected son, but every daughter is affected) C. Autosomal recessive is the most probable answer (do not invoke mutations – these can generally be taken to be extremely rare, but note that the parents of the affected females have a common ancestor in the man with two wives! Recessive traits will show up when relatives have children) D. Autosomal Dominant (50% of the progeny of affected individuals show the phenotype) E. Y linked (it is only passed from fathers to sons)...
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