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Bell Work

Bell Work. A tan cat mates with a black cat. Tan is co-dominant with black fur in cats. What is the genotype and phenotype of the offspring?. Biology – Lecture 50. Intro to Double Punnett Squares ( D ihybrid crosses). Making a Double Punnett Square.

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Bell Work

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  1. Bell Work • A tan cat mates with a black cat. Tan is co-dominant with black fur in cats. What is the genotype and phenotype of the offspring?

  2. Biology – Lecture 50 Intro to Double Punnett Squares (Dihybrid crosses)

  3. Making a Double Punnett Square • Step 1: Decide which possible allele combinations can be passed from each parent to the offspring. • Step 2: Take those 4 allele combinations and set them at the top (parent 1) and sides (parent 2) of the double punnett square. • Step 3: Cross the allele combinations in the punnett square to get the possible genotypes of the children. • Step 4: Determine the phenotype of each gene trait for the children.

  4. Mendel’s Second Law • In sexually reproducing organisms, genes generally assort independently of each other. • This means that the alleles of different genes get shuffled between parents to form offspring with many different combinations.

  5. TODAY • Step 1: Decide which possible allele combinations can be passed from each parent to the offspring.

  6. How to Determine Possible Allele Combinations • Step 1: Give each allele from each gene combination the numbers 1 and 2.

  7. Step 2: Match #1 from the first gene with #1 from the second gene. This is your first allele combination.

  8. Step 3: Match #1 from the first gene with #2 from the second gene. This is your second allele combination.

  9. Step 4: Match #2 from the first gene with #1 from the second gene. This is your third allele combination.

  10. Step 5: Match #2 from the first gene with #2 from the second gene. This is your first allele combination.

  11. Example 1 • What are the possible allele combinations from a parent that is SsYy?

  12. Practice 1 • What are the possible allele combinations from a father who is AahH?

  13. Practice 2 • What are the possible allele combinations from a mother who is KkZZ?

  14. Applying Knowledge • Use your knowledge of heterozygous, homozygous recessive, and homozygous dominant to determine the genotype of the parent and the 4 different allele combinations of the offspring.

  15. Example 1 • What are the possible allele combinations that can be made from a mother who is homozygous short (tall is dominant) and has homozygous brown eyes (blue eyes is recessive)?

  16. Practice 1 • A mother is heterozygous tall (tall is dominant), and has blue eyes (brown eyes are dominant). What are the possible alleles she can pass on to her children?

  17. Practice 2 • Determine the allele combination that can come from a father who is heterozygous brown eyed and homozygous black haired (blonde is recessive).

  18. Practice 3 • Determine the allele combination from a dog who is droopy eared (erect ears are dominant) and brown and white spotted (brown and white are co-dominant).

  19. Practice 4 • Determine the allele combination from a mouse who is heterozygous for having whiskers (no whiskers is recessive) and grey (white and black are incompletely dominant).

  20. Pop Quiz

  21. Pop Quiz • What are the 4 allele combinations that can come from the following genotype of a mother? • BbTt

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