What information can be read from a Punnett square What information can be read from a Punnett square? Use the diagram on the right to answer the questions. What are the genotypes of the two parents? Do both parents show the dominant phenotype? List the expected genotypes of the offspring. List the expected phenotype of the offspring. State the chance of having an offspring with the recessive phenotype. Does this Punnett Square illustrate a monohybrid cross? If the trait for the Punnett Square is Albinism and the allele for albinism is “a”, list the genotypes for normal pigment skin. Which person would not be at risk of causing albinism in the child? Assume the trait is controlled by simple dominance.

How is this Punnett square different from the one on the previous slide? 1. List the possible alleles that would be found in each gamete cell. 2. How many traits are involved in this Punnett square? 3. How many offspring will show only the recessive phenotype? 4. What is the chance of having an offspring with only the recessive traits? 5. How many offspring will show both dominant phenotypes? 6. How many offspring will show a dominant phenotype for Trait A and recessive phenotype for Trait B? 7. How many offspring will show a recessive phenotype for Trait A and a dominant phenotype for Trait B? Today’s lab is called….

Lab Hints Each parent is represented by a nickel and a penny. A nickel carries the alleles for height (M, m). A penny carries the alleles for melanin production, skin pigment (A,a) Tape & marker is used to mark the specific alleles on the coin. Lab indicates the genotype of a parent. For example, Aamm m A a

Finding Phenotypes & Genotypes for Two Traits 1. Simulate the inheritance of two traits using two coins. 2. Determine the expected offspring phenotype using Punnett square and mathematics. 3. Determine the observed offspring phenotype by flipping coins and recording the phenotype. 3. Write a letter to tell parents the probability of having children with the genetic disorders, albinism and dwarfism. (not assigned)

Results of Cross Between Parents with AaMm and Aamm Genotype Phenotype Combination Genotypes Number Expected For 16 Offspring For 96 Tosses Recorded Total Observed Normal skin and normal height AAMm AsMm 6 36 but midget AAmm Aamm Albino but normal aaMm 2 12 Albino and midget aamm

Number Expected For 16 Offspring For 96 Tosses Recorded Total Observed Phenotype Combination Genotypes Number Expected For 16 Offspring For 96 Tosses Recorded Total Observed Normal skin and normal height AAMM AAMm AaMM AaMm 9 54 but midget AAmm Aamm 3 18 Albino but normal aaMM aaMm Albino and midget aamm 1 16

What does the data tell us about what we observe and what we expect? The experimental data tells us what really happens. The Punnett square data tell us what most likely will happen but not definite. The Inheritance of a trait is random chance.

Types of Punnett Square Involves one gene Used only one type of letter to represent gene- HH Punnett square will have 4 boxes Simply separate the alleles (letters) to determine the gamete type produced Involves two genes Uses two types of letters to represent the genes- AABB Punnett square will have 16 boxes Use the FOIL method to determine the gametes produced. For One Trait For Two Trait

What you should Know… After doing the Congrats! Baby lab, the Two Trait Coin lab and numerous worksheets, you should be able to completely explain the possible results for a one and two trait cross. You should be able to state what a phenotypic ratio, genotypic ratio, phenotype, genotype, heterozygous, homozygous, gamete, homologous chromosome, allelle, segregation and fertilizaton all mean.