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LESSON TITLE: Mendel’s Pea Plants, Punnett Squares TIME REQUIRED: 75 min SUBJECT / STRAND: SBI 3U, Genetic Continuity GRADE: 11U EXPECTATIONS COVERED: ASSESSMENT: Overall Expectation: - demonstrate an understanding of the necessity of meiosis and describe the importance of genes in transmitting hereditary characteristics according to Mendel’s model of inheritance Specific Expectations: - predict the outcome of various genetic crosses - describe and explain the process of discovery (e.g., the sequence of studies and the knowledge gained) that led Mendel to formulate his laws of heredity Formative BACKGROUND KNOWLEDGE: SAFETY CONCERNS? - genetics terms: Genetics, trait, genes, phenotype, P generation, F1 generation, F2 generation, dominant allele, recessive allele, incomplete dominance, pure-bred, true-breeding, hybrid, Law of segregation, Law of independent assortment - formulating and interpreting basic ratios - minimal plant anatomy None LESSON DESCRIPTION: - (15 min) Complete Human Trait activity o determine ratios and percentages of dominant/recessive traits for entire class - (20 min) Introduction to Mendel and his Pea Plants o brief history of Mendel o pea plants why they were used (7 characteristics, life span) abbreviated anatomy of a flower, methods of fertilization - (30 min) Introduction to Single Trait Inheritance – Punnett Squares o work through practice problems – page 135-137, #1, 2, 3 - (10 min) Independent work on problems o Bikini Bottom worksheet o page 138, #3, 4 o extra practice – page 139 Section 4.1 - 4.2, #3ab, 4 REFLECTION: SBI 3U - Genetics Mendel and his Pea Plants Gregor Mendel (1822-1884) was an Austrian monk whose experiments with garden peas laid the foundation for the science of genetics. Mendel’s work not only explained the mechanism of gene inheritance in plants, but also provided a basis for understanding heredity in general. The charts provided show the seven different characteristics of garden pea plants that Mendel studied, as well as the alleles and possible genotypes. Keep in mind that plants with white flowers produce seeds that are yellow, and plants with violet-purple flowers produce seeds that are green. Trait Alleles (DOMINANT/ recessive) Possible genotypes Seed shape ROUND wrinkled RR or Rr rr Seed colour YELLOW green YY or Yy yy Pod shape INFLATED constricted II or Ii ii Pod colour GREEN yellow GG or Gg gg Flower colour PURPLE white PP or Pp pp Flower position on stem AXIAL (side of stem) top AA or Aa aa Plant height (stem length) TALL dwarf TT or Tt tt Practice Problems Page 138, #3 & #4 3. For each of the the table on the information: - parent - parent - parent following situations, create a Punnett square using front of the page, and determine the following phenotype genotype gametes - F1 generation genotypes - F1 generation phenotypes a) b) c) d) Two heterozygous tall parents are crossed. A heterozygous tall plan is crossed with a dwarf plant. Two plants that are heterozygous for purple flowers are crossed. A plant that is homozygous for green pods is crossed with a plant that has yellow pods. e) A plant that is homozygous for round seeds is crossed with a plant that is heterozygous for round seeds. 4. In guinea pigs, the allele for a black coat is dominant over the allele for a white coat. A black guinea pig was crossed with a white guinea pig. All F1 offspring have black coats. a) Describe how you can determine whether or not the black parent is homozygous or heterozygous for the condition. Indicate the letter you will use to represent an allele. b) If 10 offspring were produced, indicate how many you would expect to have black coat colour, if the black parent were heterozygous. SBI 3U – Genetics ___________________________ Name Bikini Bottom Genetics Scientists at Bikini Bottoms have been investigating the genetic makeup of the organisms in this community. Use the information provided and your knowledge of genetics to answer each question. 1. For each genotype below, indicate whether it is a heterozygous (He) OR homozygous (Ho). TT _____ Bb _____ DD _____ Ff _____ tt _____ dd _____ Dd _____ ff _____ Tt _____ bb _____ BB _____ FF _____ Which of the genotypes in #1 would be considered purebred? ________________________ Which of the genotypes in #1 would be hybrids? _________________________________ 2. Determine the phenotype for each genotype using the information provided about SpongeBob. Yellow body color is dominant to blue. YY _________________ Yy _________________ yy _________________ Square shape is dominant to round. SS _________________ Ss _________________ ss _________________ 3. For each phenotype, give the genotypes that are possible for Patrick. A tall head (T) is dominant to short (t). Tall = _______________________ Short = _________________________ Pink body color (P) is dominant to yellow (p). Pink body = ___________________ Yellow body = _____________________ 4. SpongeBob SquarePants recently met SpongeSusie Roundpants at a dance. SpongeBob is heterozygous for his square shape, but SpongeSusie is round. Create a Punnett square to show the possibilities that would result if SpongeBob and SpongeSusie had children. HINT: Read question #2! A. List the possible genotypes and phenotypes for their children. B. What are the chances of a child with a square shape? ______ out of _____ or ______% C. What are the chances of a child with a round shape? ______ out of _____ or ______% 5. Patrick met Patti at the dance. Both of them are heterozygous for their pink body color, which is dominant over a yellow body color. Create a Punnett square to show the possibilities that would result if Patrick and Patti had children. HINT: Read question #3! A. List the possible genotypes and phenotypes for their children. B. What are the chances of a child with a pink body? ______ out of ______ or ______% C. What are the chances of a child with a yellow body? ______ out of ______ or ______% 6. Everyone in Squidward’s family has light blue skin, which is the dominant trait for body color in his hometown of Squid Valley. His family brags that they are a “purebred” line. He recently married a nice girl who has light green skin, which is a recessive trait. Create a Punnett square to show the possibilities that would result if Squidward and his new bride had children. Use B to represent the dominant gene and b to represent the recessive gene. A. List the possible genotypes and phenotypes for their children. B. What are the chances of a child with light blue skin? ______% C. What are the chances of a child with light green skin? ______% D. Would Squidward’s children still be considered purebreds? Explain! 7. Mr. Krabbs and his wife recently had a Lil’ Krabby, but it has not been a happy occasion for them. Mrs. Krabbs has been upset since she first saw her new baby who had short eyeballs. She claims that the hospital made a mistake and mixed up her baby with someone else’s baby. Mr. Krabbs is homozygous for his tall eyeballs, while his wife is heterozygous for her tall eyeballs. Some members of her family have short eyes, which is the recessive trait. Create a Punnett square using T for the dominant gene and t for the recessive one. A. List the possible genotypes and phenotypes for their children. B. Did the hospital make a mistake? Explain your answer.