Genetics Exam Ii Bayesian Analysis

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Bayesian Analysis

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is a mathematical model to account for factors that complicate traditional Mendelian inheritance.

-Basic Mendlian probability risks can be altered for an individual based on family history, a person's age (for delayed age of onset), chromosomal test, etc.

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Risks based on inheritance patterns (theoretical risk)

Theoretical risk a person is a carrier (or not a carrier) based on the known Mendelian mode of inheritance

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Prior risk

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Take modifying information into account to determine more appropriate risk

The probability that the known events would have occurred if the person was a carrier versus the probability that these same known events would have occurred if the person was not a carrier.

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Conditional risk

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Assessing carrier risk based on family history: presence of unaffected children

The FINAL risk probability of being a carrier or not a carrier.

= Joint probability of one possibility / total possible probabilities which is the sum of the two joint probabilities of being either a carrier or a non-carrier

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Posterior risk

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The product of the prior probability and the conditional probability (for either the carrier status or the non-carrier status)

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Joint probability

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Disorder with reduced penetrance

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If a parent with an autosomal dominant disease has an unaffected child, there is a risk the child carries the mutation and is not expressing the condition.

Higher the penetrance, the less likely the unaffected child is a carrier

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Disorder with late age of onset

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The older the person is, the less likely that person is a carrier.

So the actual risk of developing the disease secreases with each year in adulthood.

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Genetic testing with known detection rates

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A common use of Bayesian analysis is with carrier testing with known carrier rates.
Example: Cystic Fibrosis