Lecture_5_-_Laws_of_Probability-1

Lecture_5_-_Laws_of_Probability-1 - Lecture 5 Lecture Laws...

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Lecture 5 Lecture 5 Laws of Probability, Chi- Laws of Probability, Chi- Square Analysis and Square Analysis and Pedigree Analysis Pedigree Analysis
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Laws of Probability Laws of Probability Genetic or genotypic ratios can also be expressed as probabilities. The outcome of a particular event can be predicted based on probabilities The probability that a zygote has a specific genotype for a particular trait can be predicted based on the laws of probability
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Laws of Probability Laws of Probability Additive Law – the sum of the probabilities of all possible outcomes of a given event is 1.0 Flip a coin: possible outcomes are Heads or Tails P(H) is 1 out of 2 or P(H) = ½ =.5 P(T) is 1 out of 2 or P(T) = ½ = .5 P(H) + P(T) = .5 + .5 = 1.0
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Laws of Probability Laws of Probability Consider the gene for plant height: 2 Alleles: D or d P(D) occurring in a gamete = ½ = .5 P(d) occurring in a gamete = ½ = .5 P(D) + P(d) = .5 + .5 = 1.0
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Laws of Probability Laws of Probability Multiplicative Law – the probability of 2 independent events occurring simultaneously is the product of their individual probabilities Flip a coin 2 times - outcome of second flip is independent of the outcome of the second flip 1st flip: P(H) = .5 P(T) = .5 2nd flip: P(H) = .5 P(T) = .5
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Laws of Probability Laws of Probability What is the probability of flipping a coin twice and getting two heads? 1 st flip possible outcomes: P(H) = .5 P(T) = .5 2 nd flip possible outcomes: P(H) = .5 P(T) = .5 Possible outcomes on both flips: HH HT TH TT P(HH) = .5 X .5 = .25 P(HT) = .5 X .5 = .25 P(TH) = .5 X .5 = .25 P(TT) = .5 X .5 = .25
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Laws of Probability Laws of Probability What is the probability of getting exactly one head in two tosses? Possible outcomes on both flips: HH HT TH TT What is the probability of getting at least one head in two tosses? Possible outcomes on both flips: HH HT TH TT
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Laws of Probability Laws of Probability What if you get 7 heads and 3 tails in 10 tosses? Does this mean laws of probability don’t work? No, remember each toss is an independent event and the outcome occurs randomly . The chances of getting exact results are low, especially with a small number of tosses. This is called chance or random deviation
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Laws of Probability Laws of Probability Suppose we flip a coin 100 times. What is the probability of getting ALL heads in 100 tosses? There is only ONE outcome where we would get
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Lecture_5_-_Laws_of_Probability-1 - Lecture 5 Lecture Laws...

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