1. Punnett Squares & Probability
What is probability?

2. Probability What is probability?
The likelihood that a particular event will occur
The principles of probability can be used to predict the outcomes of genetic crosses.

3. Punnett Squares
The gene combinations that might result from a genetic cross can be determined by drawing a diagram

4. Tt X Tt Cross
Section 11-2
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5. Allele combinations
Homozygous: organisms that have two identical (same) alleles = true-breeding for a particular trait TT tt
Heterozygous: organisms that have two different alleles = hybrids for a particular trait Tt

6. Phenotype: visible, physical characteristics
Tall or short
Genotype: not visible, genetic makeup
Homozygous or heterozygous

7. Independent Assortment
Does the gene that determines whether a seed is round or wrinkled in shape have anything to do with the gene for seed color?
NO!!!
The alleles for seed shape and seed color in pea plants do not influence each other’s inheritance

8. The Principle of Independent Assortment
Genes for different traits can segregate independently during the formation of gametes.

9. Summary of Mendel’s Principles
Inheritance is determined by genes passed from parents to offspring
Some forms of genes are dominant and others are recessive
Each offspring has two copies of a gene (alleles), one from each parent because they are segregated during gamete formation
The allele for different genes usually segregate independently of one another

10. What will happen if some alleles are neither dominant nor recessive?
What will happen if some traits are controlled by more than one gene?

11. Incomplete Dominance
When one allele is not completely dominant over another
For example: 4 o’clock plant

12. Figure 11-11 Incomplete Dominance in Four O’Clock Flowers
Section 11-3
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13. Figure 11-11 Incomplete Dominance in Four O’Clock Flowers
Section 11-3
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14. Codominance Both alleles contribute to the phenotype of the organism
For example: roan