5 & 6 Problem Solving

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1. Probability
the proportion of times a specific outcome occurs in a series of events

eg. in a pregnancy: 1/2 girl, 1/2 boy
2. Independent Events
the outcome of one event does NOT depend on outcome of other event

eg. a previous pregnancy does NOT affect a future one

each conception: 1/2 boys, 1/2 girls
3. Multiplication Rule
if 2 events are INDEPENDENT of each other, the probability of outcome of both occurrences happening is the product of each outcome

eg. the chance of having 3 children & all of them be girls = 1/2 * 1/2 * 1/2 = 1/8
• the probability of one outcome OR another is the addition of each outcome
• boy or girl = 1/2 + 1/2 = 1

• • probability of getting EITHER 2 heads in a row OR 2 tails in a row =
• (1/2 * 1/2) + (1/2 * 1/2) = 1/4 + 1/4 = 1
5. p
frequency of the dominant ALLELE in a population (present in people with both AA & Aa)
6. q
frequency of the recessive ALLELE in a population (present in people with both Aa & aa)
7. p+q =
1
8. q2
how many people have the aa genotype

• the incidence of homozygous recessive people in a population

• eg. CF (AR) has an incidence of 1/2500
• - that means 1 in every 2500 people HAS CF, so q2 = 1/2500
9. 2pq
how many people have the Aa genotype

• the incidence of heterozygous people in a population

• what you’re looking for if someone asks you what a CARRIER RATE is
10. p2
how many people have the AA genotype

• the incidence of homozygous dominant people in a population
11. How to calculate the chance that ALL children of two AR disease carriers are affected:
multiply each of their chances

eg. for 2 siblings: 1/4 * 1/4 = 1/16 chance that all are affected
12. How to calculate the chance that ALL children of two AR disease carriers are UNaffected
multiply each of their chances

eg. for 2 siblings: 3/4 * 3/4 = 9/16 chance that none of them are affected
13. How to calculate the chance that AT LEAST 1 child will be affected:
1 — NONE

eg. from above example, 1 - 9/16 = 7/16 chance at least 1 child will be AFFECTED
14. When Penetrance can be Measured
• eg. if Penetrance = 60%, then there’s a 60% chance each affected individual expresses the trait
15. What risk of complications/pregnancy loss does Amniocentesis present to a mother?
~ 0.5%

• if a child’s risk for being affected by a condition is LOWER than the risk of Amniocentesis, it’s NOT offered
 Author: mse263 ID: 322695 Card Set: 5 & 6 Problem Solving Updated: 2016-08-27 02:04:05 Tags: MedFoundationsI Genetics Exam1 Folders: MedFoundationsI,Genetics Description: Genetics Exam 1 Show Answers: