HG 16 Bayesian
Ans to 63: 1/41 X linked pattern Allison's risk to be a carrier is 1/41
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Ans to 8: Most likely: B and C (EQUAL) A : least likely
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Based on the pedigree, what is the chance that III-6 is a carrier? Condition is hemophilia A
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Carol has a son with Duchenne muscular dystrophy. There is no other family history of DMD. DNA analysis was negative for her and her son (70% of males and female carriers with DMD have an identifiable mutation). The woman's CPK is normal (70% of obligate DMD carriers have high CPK's). The woman also has two healthy sons. What is the chance that Carol's next child will have DMD?
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In which pedigree is the current pregnancy most likely to be affected with the familial autosomal recessive condition? The least likely?
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When a male is diagnosed with DMD and we do not have molecular diagnostic or other FHx info, we can conclude: __ chance that mother is a carrier __ chance that he has a de novo mutation
2/3 chance that mother is a carrier 1/3 chance that he has a de novo mutation
Ans to 59: 3/92 3/23 x ½ x ½ = 3/92
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Ans to 61= 6/1192 6/298 x 1/4 = 6/1192
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Ans to 53: 3/26 3/13 x 1/2 = 3/26 Amanda is Passes carrier on gene Daughter's risk to be a DMD carrier is 3/26
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Ans to 55: 1/22 1/11 x 1/2 = 1/22 Jane is a and passes carrier on gene
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6: Most likely: D (longer u live w/o symptoms the least likely u have HD) Least likely : a
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A family is affected with Huntington disease, an adult-onset neurologic disorder. Fifty percent (50%) of people who inherit the HD gene show some symptoms of HD by the age of 50. Betty is 50 and asymptomatic, but her father died of HD. What is the probability that Betty's son, John, inherited the HD gene?
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Allison has a sister who has a son with Hunter syndrome, an X-linked mucopolysaccharidosis. What is Allison's risk to be a carrier if she already has three healthy sons?
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Amanda has a son with Duchenne muscular dystrophy (DMD). There is no other family history of DMD. She has one healthy son and one healthy daughter. She also had a normal CPK level (70% of DMD carriers have a high CPK). What is Amanda's daughter's chance to be a DMD carrier?
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Ans to 25 = 1/80 1 x 1/2 x 1/20 x 1/2= 1/80 q^2 = 1/1600 q = 1/40 2pq = 1/20
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Ans to 2: all at equally risk for pregnancy to be affected (1/4 chance of being affected per pregnancy)
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Ans to 30 = 1/24 2/3 x ½ x [(1/8) + (1/2)] x 1/2 = 2/3 x ½ x ¼ x ½ = 1/24 mom is 2/3 because her parents are both carriers
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Ans to 31: 9/356 (prior risk = both parents are carriers) 9/89 x ¼ = 9/356
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Ans to 37: 1) 1/6 (Bayesian Analysis is NOT needed) Chance mom is carrier x pass x male child 2/3 x ½ x ½ = 1/6 2) 1/3 What is the chance that II-2 is a carrier? 2/3 x ½ = 1/3 3) 1/12 What is the chance that II-2 will have an affected child? 1/3 x ½ x ½ = 1/12
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Ans to 4: Most likely: c Least likely: d More pregnancies not affected = lower chance that the next pregnancy will be affected
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Ans to 51: 1/352 1/88 x 1/4 = 1/352 Kim and Peter Both pass are both carriers on CF gene
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Jake's sister has cystic fibrosis. DNA reveals that she has one F508 mutation but her other mutation is unidentified. Jake's DNA testing does not reveal any mutation. His wife has no family history of CF, and her DNA testing was also negative. The population carrier frequency is 1/25. Assume mutation analysis detects 90% of CF mutations. What is Jake's chance to have a child with CF?
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Jane is 28 weeks pregnant and consults a genetic counselor because her brother died of severe X-linked hydrocephalus (aqueductal stenosis). She has two unaffected brothers. An ultrasound found that her fetus is a male. Jane already has one unaffected son and one unaffected daughter. What is the chance that Jane's fetus will be affected?
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Kim and Peter have two healthy children but Kim's sister has a child recently diagnosed with CF. Peter has no family history of CF. What is the chance that Kim and Peter's next child will have CF?
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Rebecca has a sister with cystic fibrosis. Her husband, Paul, has no family history of CF. The couple already has one healthy child. What is the chance that their next child could have CF?
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Retinoblastoma (Rb), a malignant tumor of the eye may be inherited as an autosomal dominant trait. Penetrance is about 4/5 (80%). Michael's paternal grandmother, father and brother had Rb, but Michael is unaffected. What is the risk that Michael's child may develop retinoblastoma?
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Sydney's paternal grandfather died of Huntington disease (HD). Her father is 50 years old and is unaffected. Her brother was diagnosed at 32 years of age with HD. Sydney is now 30 and wants to know her chance to develop HD. Approximately 10% of HD gene carriers are clinically affected by 30, 50% by age 50, and almost 100% by age 70.
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1) Suppose a man has an AD condition that is observable at birth. What is the probability that his unborn child will be affected? 2) What if the condition is penetrant in 70% of individuals (and the other 30% may inherit the mutation and be non-penetrant)?
1) 1-in-2 or 50% 2) ½ x 7/10 = 7-in-20 or 35%
1) Fundamental probability for a non-carrier woman to have a son affected with a lethal X-linked condition is? 2) Fundamental probability for a non-carrier woman to have a daughter who is heterozygous for the X-linked mutation is? 3) Fundamental probability for a woman to be heterozygous when her mother's carrier status is unknown is?
1) μ (there is only one X for the mutation to occur on) 2) 2μ (there are two Xs for the mutation to occur on, either maternal X or paternal X) 3) 4μ (grandma carrier status us unknown)
A couple comes to you for counseling. The man's brother died of an autosomal recessive disease that has a population frequency of 1-in-40,000. A carrier screen is available (false positive rate of 10% and false negative rate of 6%). The man tests negative and the woman tests positive. What is the chance for their first child together to have the disease?
Ans: 0.26% Dad Carrier X Pass X Mom Carrier X Pass 12/102 x ½ x 94/1084 x ½ = 0.26%
1) What is the probability that II-3 will be affected with DMD? 2) What is the chance that II-2 is a carrier? 3) What is the chance that II-2 will have an affected child?
DMD is X linked recessive
Why is Bayesian Analysis IMPT for GCs?
It allows for the calculation of specific probability based upon additional family information or test results. - may dramatically change genetic risk assessments for individuals making life decisions
When we are discussing a "lethal" X-linked condition, μ = ?
the mutation rate per locus per meiosis.
