Probability and Punnett Probability and Punnett SquaresSquares

Section 11–2Section 11–2

ProbabilityProbability

The likelihood that a particular event The likelihood that a particular event will occur is called_______.will occur is called_______.

• ProbabilityProbability

ProbabilityProbability

Circle the letter of the probability that Circle the letter of the probability that a single coin flip will come up heads.a single coin flip will come up heads.

• a. 100 percent a. 100 percent

• b. 75 percentb. 75 percent

• c. 50 percent c. 50 percent

• d. 25 percentd. 25 percent

ProbabilityProbability

• Is the following sentence true or Is the following sentence true or false? false?

• The past outcomes of coin flips The past outcomes of coin flips greatly affect the outcomes of future greatly affect the outcomes of future coin flips.coin flips.

• FalseFalse

ProbabilityProbability

• Why can the principles of probability Why can the principles of probability be used to predict the outcomes of be used to predict the outcomes of genetic crosses? genetic crosses?

• The way in which the alleles The way in which the alleles segregate is completely random, like segregate is completely random, like a coin flip.a coin flip.

Punnett SquaresPunnett Squares

• How do geneticists use Punnett How do geneticists use Punnett squares?squares?

• Punnett squares can be used to Punnett squares can be used to predict and compare the genetic predict and compare the genetic variations that will result from a variations that will result from a cross.cross.

Punnett SquarePunnett Square

Complete the Punnett square to show the possible gene combinations for the F2 offspring.

Allele TypesAllele Types

• Homo - SameHomo - Same

• Hetero - OppositeHetero - Opposite

• Pheno – PhysicalPheno – Physical

• Geno - GeneticGeno - Genetic

Allele TypesAllele Types

DefinitionsDefinitions

• Organisms that have two identical allelesOrganisms that have two identical alleles

• particular trait (particular trait (TT TT or or tttt) ) HomozygousHomozygous

• Organisms that have two different allelesOrganisms that have two different alleles

• same trait (same trait (TtTt) ) HeterozygousHeterozygous

• Physical characteristic of an organism Physical characteristic of an organism PhenotypePhenotype

• Genetic makeup of an organism (Genetic makeup of an organism (TtTt) ) GenotypeGenotype

Gene ExpressionGene Expression

Are the following sentences true or Are the following sentences true or false? false?

- Homozygous organisms are true - Homozygous organisms are true breeding for a particular trait.breeding for a particular trait.

• FalseFalse

- Plants with the same phenotype - Plants with the same phenotype always have the same genotype.always have the same genotype.

• FalseFalse

Probability and SegregationProbability and Segregation

• b. b. The F2 ratio of tall plants to short The F2 ratio of tall plants to short plants produced in a cross between plants produced in a cross between two hybrid tall pea plants (two hybrid tall pea plants (TtTt) is 3 tall ) is 3 tall plants for every 1 short plant.plants for every 1 short plant.

• c. c. Mendel observed that about 3⁄4 of Mendel observed that about 3⁄4 of the F2 offspring showed the the F2 offspring showed the dominant trait.dominant trait.

• d. d. Segregation occurs according to Segregation occurs according to Mendel’s model.Mendel’s model.

ProbabilityProbability

• In Mendel’s model of segregation, In Mendel’s model of segregation, what was the ratio of tall plants to what was the ratio of tall plants to short plants in the F2 generation? short plants in the F2 generation?

• The ratio was 3 : 1.The ratio was 3 : 1.

ProbabilityProbability

• Is the following sentence true or Is the following sentence true or false? false?

• Probabilities predict the precise Probabilities predict the precise outcome of an individual event.outcome of an individual event.

• FalseFalse

ProbabilityProbability

• How can you be sure of getting the How can you be sure of getting the expected 50 : 50 ratio from flipping a expected 50 : 50 ratio from flipping a coin?coin?

• You must flip the coin many times.You must flip the coin many times.

ProbabilityProbability

17. 17. The _____ number of offspring from The _____ number of offspring from a genetic cross, the closer the a genetic cross, the closer the resulting numbers will get to resulting numbers will get to expected values.expected values.

• LargerLarger

ProbabilityProbability

Is the following sentence true or false?Is the following sentence true or false?

• The ratios of an F1 generation are The ratios of an F1 generation are more likely to match Mendelian more likely to match Mendelian predicted ratios if the F1 generation predicted ratios if the F1 generation contains hundreds or thousands of contains hundreds or thousands of individuals. individuals.

• TrueTrue