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11-2 Probability and Punnett Squares. Pg. 267. A. Genetics and Probability. 1. Probability is the likelihood that a certain event will occur. Ex: A coin toss. 2 Outcomes: Tails and Heads ½ or 50% chance. A. Genetics and Probability.
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A. Genetics and Probability • 1. Probability is the likelihood that a certain event will occur. Ex: A coin toss. • 2 Outcomes: Tails and Heads • ½ or 50% chance
A. Genetics and Probability • 3. What is the probability of getting tails three times in a row? • 4. The principles of probability can be used to predict the outcomes of genetic crosses.
B. Punnett Squares • 1. Punnett squares are used to show the possible results from a genetic cross.
B. Punnett Squares • 2. Letters represent alleles. • 3. Letters on the outside of the square represent parents. • 4. Letters on the inside represent offspring.
B. Punnett Squares • 5. Two identical letters are homozygous. Ex: BB or bb • 6. Two different letters are heterozygous. Ex: Bb • 7. Phenotypes are the physical characteristics. • 8. Genotypes are the genetic make-up.
C. Probability and Segregation • 1. G=Green g=Yellow • 2. ¼ of the F2 plants are GG. • 3. 2/4 or ½ are Gg. • 4. ¼ are gg. • 5. ¾ are green. • 6. ¼ are yellow.
D. Probabilities Predict Averages • 1. Remember, these are only predictions! • 2. The higher the number of offspring, the more likely that probability expectations are matched!
