Mendel Carefully Accumulated Data And Realized That The Principles Of Probability Could Be Used To Explain The Results.

Probability= The Likelihood That A Particular Event Will Occur. Coin Flip Two Possible Outcomes Chance of Heads Is 1 in 2 or 50%

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 !

Key Concept: The Principles Of Probability Can Be Used To Predict The Outcomes Of Genetic Crosses, Because Alleles Segregate As Completely Random Events.

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.

 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

 Capital Letters Indicate Dominant Alleles  Lower Case Letters Indicate Recessive Alleles T = Tall t = short

 Genes Containing The Same Alleles For A Trait Are Said To Be: Homozygous TTHomozygous Dominant ttHomozygous Recessive  Genes Containing Different Alleles For A Trait Are Said To Be: Heterozygous Tt

 Homozygous Organisms Are Said To Be: True Breeding  Heterozygous Organisms Are Said To Be: Hybrid

Phenotype › The Physical Appearance or Characteristics Of An Organism. Genotype › The Genetic Makeup (Alleles) Of An Organism TT or Tt

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

 Look At Fig › 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

 If Mendel Was Correct, The Ratio Of Tall To Short Will Be 3-to-1. › Which It Is! › Therefore, Mendel Was Correct. › Therefore, Segregation Is Supported By The Data.

Probabilities Predict The Average Outcome For A Large Number Of Events. Probability Does NOT Predict The Precise Outcome Of A Single Event.

This Is True In Genetics And Coin Tosses. The Larger The Sample Size – The Closer The Results To Expectations.