1. Foothill High School Science Department Intro To Genetics Probability & Punnett Squares

2. Foothill High School Science Department Gregor Mendel Mendel Carefully Accumulated Data And Realized That The Principles Of Probability Could Be Used To Explain The Results.

3. Foothill High School Science Department Genetics & Probability Probability= The Likelihood That A Particular Event Will Occur. Coin Flip Two Possible Outcomes Chance of Heads Is 1 in 2 or 50%

4. Foothill High School Science Department Genetics & Probability Probability of 3 Heads In A Row Each Toss Is An Independent Event Chance of 1 Head = ½ Chance of 3 Heads In Row = ½ x ½ x ½ = 1/8 Past Outcomes Do Not Influence Future Events !

5. Foothill High School Science Department Genetics & Probability Key Concept: The Principles Of Probability Can Be Used To Predict The Outcomes Of Genetic Crosses, Because Alleles Segregate As Completely Random Events.

6. Foothill High School Science Department Genetics & Probability

7. Foothill High School Science Department Punnett Squares

8. Foothill High School Science Department Punnett Squares 1.Define The Gametes That Will Be Produced By The Parents. 2.Place The Gametes Of One Parent Across The Top. 3.Place The Gametes Of The Other Parent Down The Side.

9. Foothill High School Science Department Punnett Squares The Gametes Represent The Alleles. Indicate The Genetic Makeup Of The F 1 Offspring By Combining The Allele From Each Parent In The Appropriate Location In The Box

10. Foothill High School Science Department Punnett Squares Capital Letters Indicate Dominant Alleles Lower Case Letters Indicate Recessive Alleles T = Tall t = short

11. Foothill High School Science Department Punnett Squares Genes Containing The Same Alleles For A Trait Are Said To Be:Genes Containing The Same Alleles For A Trait Are Said To Be:Homozygous TT Homozygous Dominant tt Homozygous Recessive Genes Containing Different Alleles For A Trait Are Said To Be: Heterozygous Tt

12. Foothill High School Science Department Punnett Squares Homozygous Organisms Are Said To Be: True Breeding Purebred Heterozygous Organisms Are Said To Be: Hybrid

13. Foothill High School Science Department Punnett Squares Phenotype –The Physical Appearance or Characteristics Of An Organism. Genotype –The Genetic Makeup (Alleles) Of An Organism TT or Tt

14. Foothill High School Science Department Punnett Squares Tt or TT (Tall Plants) One (1) Phenotype (Tall) Two (2) Genotypes True Breeding (TT) Hybrid (Tt) tt (Short Plants) One (1) Phenotype One (1) Genotype

15. Foothill High School Science Department Probability & Segregation Look At Fig. 11-7 (F 2 Generation)Look At Fig. 11-7 (F 2 Generation) –25% (1/4) F 2 Plants Are (TT) –50% (1/2) F 2 Plants Are (Tt) Therefore, 75% F 2 Plants Are Tall –25% (1/4) F 2 Plants Are (tt) Therefore, 25% F 2 Plants Are Short

16. Foothill High School Science Department Probability & Segregation If Mendel Was CorrectIf Mendel Was Correct –The Ratio Of Tall To Short Will Be 3-to-1. Which It Is!Which It Is! Therefore, Mendel Was Correct.Therefore, Mendel Was Correct. Therefore, Segregation Is Supported By The Data.Therefore, Segregation Is Supported By The Data.

17. Foothill High School Science Department Probabilities Predict Averages Probabilities Predict The Average Outcome For A Large Number Of Events. Probability Does NOT Predict The Precise Outcome Of A Single Event.

18. Foothill High School Science Department Probabilities Predict Averages This Is True In Genetics And Coin Tosses. The Larger The Sample Size – The Closer The Results To Expectations.