1. Genes & Punnett Squares Objectives 3-4

2. Genes Genes are the characteristics/traits coded in the DNA Genes are the characteristics/traits coded in the DNA Each gene is made up of 2 alleles (one from each parent) Each gene is made up of 2 alleles (one from each parent)

3. Principle of Dominance Dominant Allele Dominant Allele Always determines the physical feature of the individual. Always determines the physical feature of the individual. Upper case Letter (i.e. B or T). Upper case Letter (i.e. B or T). Recessive Allele Recessive Allele Only determines the physical feature of the individual when there is no dominant allele. Only determines the physical feature of the individual when there is no dominant allele. Lower case letter (i.e. b or t). Lower case letter (i.e. b or t).

4. Genotype and Phenotype The genotype of an individual is the description of the genetic information (DNA, Alleles) The genotype of an individual is the description of the genetic information (DNA, Alleles) The phenotype of an individual is the physical features made by the genotype (what they look like, a picture) The phenotype of an individual is the physical features made by the genotype (what they look like, a picture)

5. Allele Combinations If both alleles are the same, the gene is called homozygous If both alleles are the same, the gene is called homozygous BB = homozygous dominant BB = homozygous dominant bb = homozygous recessive bb = homozygous recessive If the alleles are different, the gene is called heterozygous. (Bb) If the alleles are different, the gene is called heterozygous. (Bb) Is heterozygous and homozygous an example of genotype or phenotype? Is heterozygous and homozygous an example of genotype or phenotype?

6. Label the following as homozygous dominant, homozygous recessive, or heterozygous. 1. BB 2. Aa 3. nn 4. Kk 5. GG 6. ff 7. qq 8. Hh

7. Probability and Punnett Squares Meiosis separates the alleles of a parent into different sex cells (gametes). Meiosis separates the alleles of a parent into different sex cells (gametes). Example: Dad is heterozygous for Brown hair over blonde hair = Bb (B = brown / b = blonde) Example: Dad is heterozygous for Brown hair over blonde hair = Bb (B = brown / b = blonde) Through meiosis, these alleles are copied and separated into 4 sperm. Through meiosis, these alleles are copied and separated into 4 sperm. B Bb b

8. Single Trait Crossing A Punnett Square can help you find out the trait of a child A Punnett Square can help you find out the trait of a child Example: Dad is heterozygous (Bb) for Brown hair over blonde hair. Mom is also heterozygous (Bb) for brown hair over blonde hair. Example: Dad is heterozygous (Bb) for Brown hair over blonde hair. Mom is also heterozygous (Bb) for brown hair over blonde hair.

9. Dad’s Alleles Mom’s alleles B B b b Setup the Punnett Square

10. Dad’s Alleles Mom’s alleles B B b b BBBb bb 4 possible offspring

11. Interpreting Results ¼ or 25% chance of an offspring with homozygous dominant genes for brown hair. ¼ or 25% chance of an offspring with homozygous dominant genes for brown hair. ½ or 50% chance of an offspring with heterozygous genes for brown hair. ½ or 50% chance of an offspring with heterozygous genes for brown hair. ¼ or 25% chance of an offspring with homozygous recessive genes for blond hair. ¼ or 25% chance of an offspring with homozygous recessive genes for blond hair.

12. You try it! 1. Mom is heterozygous for Brown eyes over blue eyes. (Ee) Dad is homozygous recessive with blue eyes. (ee) What are the probabilities for the children’s genotypes? What are the probabilities for the children’s phenotypes?

13. Setup the Punnett Square Dad’s Alleles Mom’s alleles e E e e

14. Setup the Punnett Square Dad’s Alleles Mom’s alleles e E e e Ee ee 4 possible offspring

15. Results: ½ or 50% of the children would inherit heterozygous genes for Brown eyes (Ee) ½ or 50% of the children would inherit heterozygous genes for Brown eyes (Ee) ½ or 50% of the children would inherit homozygous recessive genes for Blue eyes (ee) ½ or 50% of the children would inherit homozygous recessive genes for Blue eyes (ee)

16. Hmmm… Is it possible for two Brown haired parents to produce a blond child? Explain. Is it possible for two Brown haired parents to produce a blond child? Explain. Is it possible for 2 blue eyed parents to produce a brown eyed child? Explain. Is it possible for 2 blue eyed parents to produce a brown eyed child? Explain. Can you figure out your genotype for hair color? How do you know? Can you figure out your genotype for hair color? How do you know?

17. Review Questions 1. How is meiosis related to heredity? 2. What is the difference between heterozygous, homozygous dominant, and homozygous recessive? 3. Is it possible for two brown haired parents to produce a blond child? Explain.

18. Review cont… 4. What is the difference between genotype and phenotype? 5. What are the chances that two heterozygous parents with Brown hair(Bb) produce a child that is also heterozygous?

19. Review cont… 6. In pea plants, round peas are dominant over wrinkled peas. (R and r). What would the offspring of a homozygous dominant, and a homozygous recessive cross look like? 7. If the offspring from question #6 were to pollinate each other (as plants often do), what would be the genotype probabilities for the offspring?

20. Two Trait Crosses When looking at two different genes in the same cross, 4 alleles are used When looking at two different genes in the same cross, 4 alleles are used For instance, a heterozygous haired(Bb), and homozygous recessive eyed(ee) parent would be Bbee. For instance, a heterozygous haired(Bb), and homozygous recessive eyed(ee) parent would be Bbee. Through meiosis, there would be 4 possible allele combinations in the sex cells. Through meiosis, there would be 4 possible allele combinations in the sex cells.

21. bebeBeBe FOIL! Just like in math class, the first, outside, inside, and last rule can help you get the answer Just like in math class, the first, outside, inside, and last rule can help you get the answer (B b) (e e) (B b) (e e) These alleles would produce these four combinations. These alleles would produce these four combinations.