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Wednesday – September 23, 2009

Wednesday – September 23, 2009. Objectives : SWBAT create and analyze Punnett Squares. Catalyst : What is the difference between a gene and an allele? How do we represent dominant alleles? Recessive alleles?. Agenda . Catalyst Review Making Babies Lab (GASP!) Punnett Squares

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Wednesday – September 23, 2009

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  1. Wednesday – September 23, 2009 Objectives: • SWBAT create and analyze Punnett Squares. Catalyst: • What is the difference between a gene and an allele? • How do we represent dominant alleles? Recessive alleles?

  2. Agenda • Catalyst Review • Making Babies Lab (GASP!) • Punnett Squares • Guided Practice • Independent Practice • Closing

  3. Catalyst • A gene codes for a trait- eye color, ear lobes, dimples, etc. • An allele is a different version of a gene. • Ex: Brown vs. Blue eyes • Ex: Attached vs. Free hanging earlobes • Ex: Dimples vs. No dimples

  4. Traits Allele Homozygous Heterozygous Dominant Recessive Check your awesome notes! Review Yesterday’s Vocab

  5. Remember… • GENOTYPE = combination of alleles inherited from the parents (thegenes) • PHENOTYPE = physicalexpression of the trait

  6. Today, you are going to have 20 kids. • What? • Yes. In 15 minutes, you will have 20 kids. • You will need to find someone in the class to mate with. • We will demonstrate how this works.

  7. Key Point #1 • Punnett Squares are diagrams that are used to predict the genotypes of offspring.

  8. Probability…not EXACT • It is important to note that Punnett Squares only give probabilities for genotypes • It doesn’t give you the EXACT outcomes • You will see when we start creating our Punnett Squares

  9. Key Point #2 • You can never know for sure what offspring will look like, you can only predict based on probability.

  10. Key Point #3 • We refer to the parent generation as P1 and the offspring of that generation as F1. P1 F1

  11. Before we get started… • CAPTIALIZED letters are DOMINANT • lowercase letters are recessive Examples: B = brown hair (DOMINANT) b = blonde hair (recessive) Y = yellow (DOMINANT) y = green (recessive) P = purple (DOMINANT) p = white (recessive)

  12. Before we get started… D = dimples d = no dimples Homozygous dominant Genotype: DD Phenotype: have dimples Homozygous recessive Genotype: dd Phenotype: no dimples Heterozygous Genotype: Dd Phenotype: have dimples

  13. Before we get started… B = brown eyes b = blue eyes Homozygous dominant Genotype: BB Phenotype: brown eyes Homozygous recessive Genotype: bb Phenotype: blue eyes Heterozygous Genotype: Bb Phenotype: brown eyes

  14. Big Pun-nett • Let’s make our own. First things first, draw yourself box and split it into 4 squares.

  15. Punnett like its Hot • Now, read the problem and find the parents’ genotypes. • *Remember, use the first letter of the dominant trait. A homozygous dominant brown eyed male mates with a blue eyed female. BB bb

  16. Punnett Squares are COOL • Parents go on the top and on the left (keep them together) • It doesn’t matter which parents goes on the top or the left B B b b b b

  17. Punnett Square Dance • Now, bring em together. • The four boxes represent the possible kids. B B Bb Bb b b Bb Bb

  18. Just Punnett! • Now, we analyze. • Use quarters to figure out percentages. B B • How many homozygous dominant do we have? 0% • How many heterozygous do we have? 100% • How many homozygous recessive do we have? 0% Bb Bb b b Bb Bb

  19. Punnett baby one more time • Lastly, figure out percentages by phenotypes. • What percentage will have brown eyes? 100% • What percentage will have blue eyes? 0% B B Bb Bb b b Bb Bb

  20. Let’s do one more on the board • A heterozygous dimpled male mates with a heterozygous dimpled female.

  21. Whiteboard Guided Practice: Seed Shape • Solve the following Punnett Square. • A homozygous dominant round seeded plant is crossed with a heterozygous wrinkled plant. • Find the genotype and phenotype probabilities. R R RR RR R Rr Rr r R = round r = wrinkled

  22. Guided Practice: Earlobes F = free f = attached • Solve the following Punnett Square • A male with attached earlobes mates with a heterozygous free hanging earlobe female. • Find the genotype and phenotype percentages. F f Ff ff f Ff ff f

  23. Oh, how we love Spongebob! • Your teacher will now pass out the GP & IP “Punnett Squares – Spongebob Style” worksheets • We’ll do some of them together…then you get to try the rest on your own!

  24. Wrap Up • Punnett Squares are diagrams that are used to predict the genotypes of offspring. • You can never know for sure what offspring will look like, you can only predict based on probability. • We refer to the parent generation as P1 and the offspring of that generation as F1.

  25. Exit Question Create a Punnett Square. Do a cross of two heterozyous parents for brown eyes. List the genotypes & phenotypes probabilities of both the P1 and F1 generations.

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