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Drawing from the Deck of Genes Probability & Genetics

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PROBABILITY Likelihood that a specific event will occur Can be determined by a formula: Probability# of one kind of possible outcome total Probability = # of one kind of possible outcome total # of all possible outcomes # of all possible outcomes

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Predicting a chance event Use probability to figure out your chances of pulling cards out of a deck. Predict possibility of genetic traits appearing in offspring

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1.What is the probability of a coin landing heads up? 1/2 2.What is the probability of a coin landing tails up? 1/2 3/6 = 1/2 3. You have a deck of cards ( 52 cards). What is the probability of picking two red queens? 2/52 X 2/52 = 4. A die has six sides. What is the probability of rolling an odd number? 1,3,5

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FIRST LAW OF PROBABILITY Probability has NO MEMORY 100 times heads? 6. If you toss a coin 100 times, what is the probability it will land on heads? 10 times tails 7. You have tossed a coin 10 times and each time it has landed on heads, what is the probability the next toss will land tails up? 1/2 1/2

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FIRST LAW OF PROBABILITY The outcome (result) of a chance event is never influenced by previous results. EXAMPLE:EXAMPLE: Chances of have a boy?Chances of have a boy? After having 3 or 4 girls, what are the chances for a boy ?After having 3 or 4 girls, what are the chances for a boy ? 1/2 still 1/2

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Second Law of Probability: PRODUCT RULE MULTIPLICATION PRODUCTProbability of 2 chance events occurring together is the MULTIPLICATION PRODUCT of the individual probabilities. two heads 8. What is the probability of tossing two heads in a row? ½ x ½ = four heads 9. What is the probability of tossing four heads in a row? ½ x ½ x½ x ½ =

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PUNNETT SQUARES Can be used to PREDICT Important in Genetics because: Used to predict FREQUENCY Of gametes and offspring Valid only when LARGE NUMBERS are used gametes

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Genetics & Probability Mendels Laws: Segregation Independent assortment Reflect same laws of probability that apply to tossing coins or rolling dice

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The rule of multiplicationThe rule of multiplication To find the probability of 2 chance events occurring together Multiply product of their separate probabilities ½ B X ½ b = ¼ Bb Second Law of Probability Figure 9.13 F 1 Genotypes B b female B b male Formation of eggs Formation of sperm 1/21/2 B B 1/21/2 b 1/21/2 B B 1/41/4 ( 1 / 2 1 / 2 ) 1/21/2 b bB 1/41/4 Bb 1/41/4 bb 1/41/4 F 2 Genotypes

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2 nd Law of Probability ace 4/52 (1/13)Ex: If your chances of pulling an ace from a deck of cards is 4/52 (1/13) and heart13/52 (1/4)Your chances of pulling a heart is 13/52 (1/4), then your chance of getting an ace of hearts is: 1/13 x ¼ = 1/52

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