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Learn about probability and Punnett squares in genetics. Understand how to predict outcomes using probability principles and genetic crosses. Explore the concepts of alleles, homozygous, heterozygous, phenotypes, and genotypes. Discover how probabilities predict averages in genetics.
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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!
