1. Genetic Crosses...and Zygosity

2. Heterozygous: Having two DIFFERENT alleles for a trait. Homozygous: Having two of the SAME allele for a trait.

3. Genetic Crosses Punnett Square: A chart showing the possible genotypes of potential offspring.

4. Genetic Crosses Monohybrid Cross: Punnett Square testing the possibility of one gene

5. Genetic Crosses Dihybrid Cross: Punnett Square testing the possibility of two genes

6. Practice: Zygosity Look at the two parents and four offspring in this Punnett Square. List and identify which plants are heterozygous and which are homozygous. Pollen (Bb):___________ Pistil (Bb):____________ Offspring 1 (BB):_______ Offspring 2 (Bb):_______ Offspring 3 (Bb):_______ Offspring 4 (bb):_______

7. Practice: Ratios & Probabilities 1) What is the ratio of purple flower offspring to white flower offspring? 2) What is the probability (%) that the offspring will have purple flowers? What is the probability (%) that the offspring will have white flowers?

8. Predicting A couple has four offspring. Three of the offspring can roll their tongue. One of the offspring cannot. With your partner, predict the genotype and phenotype of the parents. Use “R” for rolling allele and “r” for non-rolling. Parent 1Parent 2 Genotype (Alleles) __ __ __ __ Phenotype (Ability) ____________________

9. Draw and complete a Punnett Square for the tongue-rolling family described on the previous slide.

10. The offspring from the top left corner of the previous Punnett Square grows up and marries a heterozygous partner. Predict the offspring from this new couple by completing a new Punnett Square. Question What is the probability that some of the offspring will NOT be able to roll their tongues?

11. Analyze: Use the diagram below to explain why offspring sometimes do NOT look like their parents.

12. Create Your Own Scenarios: Choose organisms to breed. Identify the genotypes and phenotypes of the parent organisms. Identify the dominant and recessive alleles. Create a Punnett Square. Give the ratio and probability of the potential offsprings’ genotypes and phenotypes. Compete at least three different scenarios with all of the above information.

13. Scenario For Example: Bear Eye Color Brown Eye Allele: B (dominant) Green Eye Allele: b (recessive) ParentsPhenotypeGenotype Bear 1Brown EyesBB (homozygous dominant) Bear 2Green Eyesbb (homozygous recessive) Punnett SquareBB bBb b Phenotype Ratio: 4 brown eyes : 0 green eyes Probability: 100% brown eyes 0% green eyes Genotype Ratio: 4 heterozygous : 0 homozygous Probability: 100% heterozygous 0% homozygous