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Section 6-5 Part 1 Punnet Squares

Section 6-5 Part 1 Punnet Squares. Write everything that is underlined. A. Dominant vs. Recessive. Dominant traits: the ones you can see Recessive traits: are hidden by dominant Rule of Dominance : When a dominant trait is present the recessive trait is hidden. Phenotype :.

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Section 6-5 Part 1 Punnet Squares

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  1. Section 6-5 Part 1Punnet Squares Write everything that is underlined

  2. A. Dominant vs. Recessive • Dominant traits: the ones you can see • Recessive traits: are hidden by dominant • Rule of Dominance: When a dominant trait is present the recessive trait is hidden

  3. Phenotype: • The way an organism looks. • No matter what genes are present, phenotype of a tall pea plant is tall and a short pea plant is short

  4. Genotype: • The gene combination of an organism • It consists of 2 alleles • For example: • Pure dominant, 2 dominant genes • Pure recessive, 2 recessive genes • Hybrid, 1 dominant and 1 recessive gene

  5. Homozygous: • When the 2 alleles are the same • 2 dominant genes = Homozygous dominant • 2 recessive genes = Homozygous recessive

  6. Heterozygous: • When the 2 alleles for a trait are different • It’s a hybrid • 1 dominant gene and 1 recessive gene

  7. Punnet Square time!!!

  8. Punnett Squares • Punnett squares allow you to predict the ratios or percentages of offspring possible in a cross.

  9. Punnett SquareLettering • Dominant Genes • Always get capital letters. • The letters will be the 1st letter of the trait. • Recessive Genes • Always get lower case letters. • The letter used is the same as the one used for the dominant gene.

  10. Punnett Squares All problems will consist of 5 steps: • Labeling dominant and recessive letters • The Cross- Who are the parents • The Square- draw and fill in the square • Genotype ratios or percentages • Phenotype ratios or percentages

  11. Example Problem:Red flowers are dominant over purple flowers in a certain type of plant. What will the possible genotypes and phenotypes of the offspring of a hybrid red flower and a purple flower?There are five steps to this problem

  12. Step 1: Label the dominant and recessive traits R = Red flower r = Purple flower

  13. Step 2: Write the genotypes of each parent to be crossed Purple (since it is recessive it has to be homozygous) Hybrid Red (means heterozygous) Rr rr Rr x rr

  14. Step 3: Set up the punnett square. Each parent will give up one gene or the other so there will be one gene per box for each parent Rr r r Rr rr Rrrr

  15. Rr r r Rrrr Rrrr Step 4:Analyze the genotypes 2 of the 4 (50%) offspring will be pure recessive 2 of the 4 (50%) will be hybrids

  16. Rr r r Rrrr Rrrr Step 5: Analyze the phenotypes 50% of the offspring will be red 50% of the offspring will be purple

  17. Now try one on your own • Tall plants are dominant over short plants in a tomato plant. What will the possible genotypes and phenotypes of the offspring of a Homozygous Tall plant and a Homozygous short plant?

  18. Step 1: Label the dominant and recessive traits T = Tall plant t = short plant Remember, it’s NOT T and S

  19. Step 2: Write the genotypes of each parent to be crossed Homozygous Short (homo means same) Homozygous Tall (homo means same) TT tt TT x tt

  20. Step 3: Set up the punnett square. Write the parents first T T t t TtTt TtTt

  21. T T t t TtTt TtTt Step 4:Analyze the genotypes 4 of the 4 (100%) offspring will be heterozygous (or hybrid) for plant height

  22. T T t t TtTt TtTt Step 5: Analyze the phenotypes 100% of the offspring will be Tall because having at least one T makes it tall because T is dominant over short (t)

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