Drawing from the Deck of Genes Probability & Genetics.
Transcript of Drawing from the Deck of Genes Probability & Genetics.
Drawing from the Deck of GenesDrawing from the Deck of Genes
Probability & Genetics
PROBABILITY• Likelihood that a specific event will occur
• Can be determined by a formula:
ProbabilityProbability = # of one kind of possible outcome total# of one kind of possible outcome total
# of all possible outcomes # of all possible outcomes
Predicting a chance eventPredicting 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
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 =2/52 X 2/52 =4. A die has six sides. What is the probability of rolling an odd number?
1,3,5
FIRST LAW OF PROBABILITY
• Probability has NO MEMORY
6. If you toss a coin 100 times100 times, what is the probability it will land on heads?heads?
7. You have tossed a coin 10 times10 times and each time it has landed on heads, what is the probability the next toss will land tails tails up?
1/21/2
1/21/2
FIRST LAW OF PROBABILITYFIRST 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, After having 3 or 4 girls, what are the chances for a what are the chances for a boy ?boy ?
1/21/2
still 1/2still 1/2
Second Law of Probability: PRODUCT RULESecond Law of Probability: PRODUCT RULE
• “Probability of 2 chance events occurring together is
the MULTIPLICATION PRODUCTMULTIPLICATION PRODUCT of the individual probabilities.”
8. What is the probability of tossing two headstwo heads in a row?
½ x ½ =½ x ½ =
9. What is the probability of tossing four headsfour heads in a row?
½ x ½ x½ x ½ =½ x ½ x½ x ½ =
PUNNETT SQUARES
• Can be used to PREDICT
Important in Genetics because:Important in Genetics because:
Used to predict FREQUENCY Of gametes and offspring
Valid only when LARGE NUMBERS are used
gametesgametes
Genetics & Probability
• Mendel’s Laws:
Segregation
Independent assortment
Reflect same laws of probability that apply to tossing coins or rolling dice
• The rule of The rule of multiplicationmultiplication
• 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
F1 Genotypes
B b female B b male
Formation of eggs Formation of sperm
1/2
B B
1/2
b
1/2B B
1/4
(1/2 1/2)
1/2
b
b B
1/4
B b
1/4
b b
1/4F2 Genotypes
22ndnd Law of Probability Law of Probability
• Ex: If your chances of pulling an ace ace from a deck of cards is 4/52 (1/13)4/52 (1/13) and
• Your chances of pulling a heartheart is 13/52 (1/4)13/52 (1/4) , then your chance of getting an ace of hearts is:
• 1/13 x ¼ = 1/52